The Unicorn Project: A Novel about Digital Disruption, Redshirts, and Overthrowing the Ancient Powerful Order by Gene Kim
My rating: 4 of 5 stars

For full disclosure I received a free copy of The Unicorn Project in advance of publication in exchange for a review. The content of the review are still my own independent thoughts.

The Unicorn Project is the second book about Parts Unlimited set at the same time as The Phoenix Project, whereas the initial book looked more at Devops this book looks from the perspective of a developer. As with the first book it is written in a very engaging manner.

Near the start of the book we are welcomed to The Phoenix Project by Maxine with one of her first challenges of getting the project to run on her machine, having been in a place where it’s taken a week to get projects to run I immediately empathised with the challenge. From there the book presents a few concepts throughout the story. In the first part of the book it focuses on the Five Ideals :

1. Local and Simplicity – things should be easy to understand and pickup
2. Focus, Flow and Joy – people should be able to actually get on with the job
3. Improvement of Daily Work – always striving to remove process bottlenecks
4. Psychological Safety – innovation is risky so people must be safe to take risks
5. Customer Focus – a focus on value for the customer

The book briefly talks about the functional practice of immutability, the importance of data as “the new oil” and it makes two other points and cross functional teams.

From Zone to Win they look at ways the business can innovate by looking at “Horizon 3” projects (more speculative R&D) in addition to their core bussiness i.e. “Horizon 1” (bussiness as normal). For completeness here “Horizon 2” is the transformation where the core bussiness might need to be shaken to be able to cope with the new innovations.

The other concept which is worth mentioning is the idea of Core vs Context. “Core” is something which is core and unique to your bussiness, “Context” are things which you bussiness needs to operate but would likely be better to buy in as a service rather than run & maintain or develop in house. One tool which I found quite interesting on this was the Wardley map plotting Commodity vs Value to identify which you should develop and which just to buy.

The Trusted Advisor by David H. Maister, Charles H. Green, Robert M. Galford
My rating: 4 of 5 stars

This book is quite focused on the bussiness service of being an advisor however, I feel, that in companies we are all advisors to other people and as such there are a few key points that are relevant to nearly everyone. For an advisor to be effective it means that they have to be listened to – as such this is much more about the personal relationship rather than simply technical understanding.

Build Trust and a Relationship

Advising is very personal, there needs to be a high level of trust for it to be effective. The book proposes that Trustworthiness contains

• Credibility – context expertise through accuracy and completeness over time. By:
  • Being truthful
  • Never exaggerating, even things like “our best people”
  • Show you have energy and care about their topic
  • Network people/bring others together to talk directly
  • When you don’t know say so quickly
  • Provide some examples of your work in advance
  • Relax, you know more than you think you do if not then don’t be there
  • Do your homework
  • Don’t show off
• Reliability – be dependable and consistent. By:
  • Make specific commitments on small things and deliver quick
  • Send materials over in advance for review to save time
  • Ensure meetings have clear goals, not just agendas, and complete the goal
  • Match the clients fit and feel over terminology, format etc will save them time
  • Review agendas with the client to ensure they feel their time is well spent
  • Reconfirm scheduled events and notify of rescheduling as soon as possible
• Intimacy – with someone you can talk about difficult topic and feel they care
  • Take courage and show trust first
  • Show candor as well, don’t be afraid to debate actively
  • Find fun and fascination by getting to the emotions of the decisions
  • Take care how you push – right topic, right time, right phrasing of questions.
  • Practice in advance to feel how you think things will land
  • To reduce bussiness risk you have to take a personal risk to grow intimacy.
  • One of you has to move first and it’s going to be you.

and is reduced by

• Self focus – there is nothing worse than feeling the advisor cares about themselves more than the customer

Provide Advice

The key part with providing advice is to think from the client perspective – not just to provide advice but to provide options in a way that it is clear to them from which they can choose a direction based on your recommendation, shows a deep understanding of the bussiness and political world they are in and addresses any concerns so that the advice can be adopted.

• Engage
  • Where there ideas worth talking about and an advisor worth talking to
  • Engagement is not a one time thing but regular to check in with old clients
• Listen
  • Listening for what is said and unsaid to fully understand the client and problem
• Frame
  • The advisor helps the client crystalise the problem and clarifying the many problems
  • Consists of formulating problem statements, hypothesis and points of view built around what is valuable for the client
• Envision
  • Understanding what are we really aiming for?
  • What will it look like when we get there?
  • How will we know when we are there?
• Commit
  • To understand what it will take to get to the vision
  • For the client to buy into the change

Leadershift: The 11 Essential Changes Every Leader Must Embrace by Maxwell John
My rating: 5 of 5 stars

For me this was a book which resonated very well with my thoughts and opinions so it was quite an enjoyable read and one I would recommend.

• Focus: from soloist to conductor – it’s not about you its about the team
  • Going slower so you can go further – you have to work with others so they can grow
  • Recognise you need others – working with people not against them
  • Making the effort to understand others – helping people succeed
  • Wanting others to shine more than you do – when others shine you deliver
  • Helping others to become better every day – supporting others growth
• Personal development: from goals to growth – its about always striving to get better
  • Inside growth – growth results in better performance not targets
  • Growth in a few vital things – Relationships, Leadership, Growing others and a positive attitude
  • Growth without a finish line – continuous growth
• Cost: from perks to price – its not about what you get its about what you give
  • Reality – everything worthwhile is uphill
  • Example – leaders must climb the hill first
  • Consistency – never get to stop climbing
• Relational: from pleasing people to challenging people – your aim is not to be liked but to grow people
  • Shift from what you gain to how you can help, improve your organisation
  • Value people so they put in their best, serve them, empower them, motivate them
  • Work to set expectations up front
  • Ask yourself the hard questions first
  • When a tough conversation is needed, do it right
  • 25% will support you, 50% are undecided, 25% will resist change – support the 50% join the supporting 25%
  • Balance care with candor

• Abundance: from maintaining to creating – it’s about pushing forward and not resting
  • What zone are you in?
    • Coasting – doing as little as possible
    • Comfort – doing what you have always done
    • Challenge – do what you’ve not done before
    • Creative – think what I’ve never thought before
  • Get creative
    • Fuel Passion
    • Celebrate Ideas
    • Foster Autonomy
    • Encourage Courage
    • Minimise Hierarchy
    • Reduce Rules
    • Fail Forward
    • Start Small
• Reproduction: from ladder climbing to ladder building – from just your success to helping others succeed
  • How high will others go with help?
• Communication: from directing to connecting – from telling people what to do to helping them by working together

• Improvement: from team uniformity to team diversity – there is power in diversity
  • Diverse teams fill in knowledge gaps
  • Diverse teams have different perspectives
  • Diverse teams have different experiences
• Influence: from positional authority to moral authority – for people to want to follow you because of your reputation for excellence
  • There are many types of authority – natural, positional, knowledge, situational, relational, proximity, success, mentoring and seniority authority.
  • Levels of authority
    1. Position – people follow because they have to
    2. Permission – people follow because they want to
    3. Production – people follow because you demonstrate competence
    4. People Development – people follow because you help them become competent
    5. Pinnacle – people follow because you have a reputation for excellence
• Impact: from trained leaders to transformational leaders

• Passion: from career to calling

Peak: Secrets from the New Science of Expertise by K. Anders Ericsson, Robert Pool
My rating: 3 of 5 stars

Fundamentally the book is highlighting that the people who can achieve more do so by focussing on developing skills through deliberate practice which is at odd to the more standard approach of teaching knowledge. This is because it is easier to teach and examine knowledge, however knowledge itself is not useful – the mental model so that you can perform skills are what you actually need. The book presents that the best way we know to build these mental models are through practice.

Deliberate practice is different to just doing something – just doing something longer does not automatically make you better at it. Just repeating something does not make you better and more junior people will likely have more up advanced teaching which they could be ahead of you.

Deliberate Practice is the best way to develop skills. Identifying areas you want to improve and focussing on actively getting better using measurable goals & data to provide feedback and committing regular dedicated time to the practicing pushing yourself beyond your comfort zone.

Ideally working with the best to understand their approaches will speed up your acceleration. When you hit plateaus try various techniques to try to find new mental models to go further.

Natural talent does not exist. There is no link between IQ and ability in e.g. Chess. The only places where there is a link between IQ and the result is where IQ is used as an initial filter – meaning we are missing out on people who could be very successful.

It Doesn’t Have to Be Crazy at Work by Jason Fried, David Heinemeier Hansson
My rating: 4 of 5 stars

This book is specifically about the way their start up is run, which is great but if you have external shareholders etc then some of the tips may be harder to do. If you are trying to carve out your own corner of calm there are still items in the list of tips can still be useful.

Your company is a product. Yes, the things you make are products (or services), but your company is the thing that makes those things. That’s why your company should be your best product.

• Curb Your Ambition
  • Bury the hustle – busy should not be the badge of honor you have to enjoy life
  • Happy pacifists – work is not about big fights, be content with your own world
  • Our goal: No goals -you don’t need fake goals to achieve something great
  • Don’t change the world – set out to do good work in a fair way
  • Make it up as you go – don’t try to plan out too much, let things evolve
  • Comfy’s cool – discomforts not the aim, delivering productively is
• Defend Your Time
  • 8’s enough, 40’s plenty – cut out what’s unnecessary then you have time
  • Protectionism – protect what matters, your employees time and attention
  • The quality of an hour – make quality time, like long 3-4 hours of concentration
  • Effective > Productive – when you’ve finished stop, don’t fill time unnecessarily
  • The outwork myth – don’t try to out work others by working longer its a myth
  • Work doesn’t happen at work – make a way to let work happen at work
  • Office hours – set aside time to help people on a schedule, not 24/7
  • Calendar Tetris – make booking meeting tough so only key meetings happen
  • The presence prison – stop keeping people updates where you are just work
  • I’ll get back to you whenever – don’t expect immediate responses
  • Fomo? Jomo! – keep informed in a condensed form not continuously
• Feed Your Culture
  • We’re not family – the best companies support your time with your family
  • They’ll do as you do – workaholism is a contagious disease, lead by example
  • The trust battery – build the trust battery it’s key to work relations
  • Don’t be the last to know – be proactive finding small issues before they grow
  • The owner’s word weighs a ton – realise the weight of your words on people
  • Low-hanging fruit can still be out of reach – thing appearing easy might not be
  • Don’t cheat sleep – nearly everything can wait until morning
  • Out of whack – allow people to balance, as in give and take not just give
  • Hire the work, not the résumé – see what people have done not just their CV
  • Nobody hits the ground running – everyone takes time, there are no quick wins
  • Ignore the talent war – grow and nurture your own tallent
  • Don’t negotiate salaries – pay the same for the same work, pay market rate
  • Benefits who? – give benefits to get people out the office not stuck in it
  • Library rules – around working areas treat them like libraries to get things done
  • No fakecations – actual disconnection to revitalise
  • Calm goodbyes – explain why people leave so people don’t fear they are next
• Dissect Your Process
  • The wrong time for real-time – real-time sometimes, asynchronous most times
  • Dreadlines – dates are fine but allow scope to be cut rather than over working
  • Don’t be a knee-jerk – don’t meet, write. Don’t react, consider.
  • Watch out for 12-day weeks – watch for weekend working
  • The new normal – things become the norm quickly, don’t “just this time”
  • Bad habits beat good intentions – start as you want the culture to be
  • Independencies – don’t wait for web & iOS.. to be ready release independently
  • Commitment, not consensus – “disagree & commit”. Decide, explain, go
  • Compromise on quality – not everything need to be “airworthy” but “fine”
  • Narrow as you go – as you progress narrow the scope of what you are doing
  • Why not nothing? – doing nothing can be the hardest choice but worth it
  • It’s enough – don’t flog yourself, what is good enough that people are happy
  • Worst practices – there is no single best way so don’t just adopt best practice
  • Whatever it doesn’t take – “what will it take?” not “whatever it takes”
  • Have less to do – if it does not add value then stop doing it
  • Three’s company – three is the perfect number for meetings, not more or less
  • Stick with it – get things finished or take a break but don’t move on till it done
  • Know no – you can change your mind, but if you say yes then you can’t
• Mind Your Business
  • Risk without putting yourself at risk – measure risk and gamble with care
  • Season’s greetings – work with the seasons, shorter in summer etc
  • Calm’s in the black – don’t push too hard, enjoy the calm and grow with it
  • Priced to lose – don’t become dependent on a key account think product
  • Launch and learn – don’t use focus groups get your product in use
  • Promise not to promise – it ties your hands and reduces your options
  • Copycats – that’s life move on, your direction not a snapshot in time is key
  • Change control – don’t force everyone to upgrade, they can stay comfy
  • Startups are easy, stayups are hard – don’t burn out, slow and steady wins
  • “No big deal” or “the end of the world”? – one for you one for the customer
  • The good old days – you don’t have to grow, if you happy stay there

Essential Kanban Condensed by David J. Anderson & Andy Carmichael
My rating: 5 of 5 stars

This is a really brief but neat book, although it goes into the Kanban board/cards etc the piece which I felt was a very nice and useful summary was its values, principles etc.

Kanban values

• Transparency – The belief that sharing information improves the generation of business value.
• Balance – The understanding that different aspects, viewpoints, and capabilities all must be balanced for effectiveness.
• Collaboration – The focus on the way people work together.
• Customer Focus – Knowing the value which the system brings to its users.
• Flow – The realisation that work is a flow of work leading to value generation, whether continuous or episodic. Improving the flow improves generation of value.
• Leadership – In Kanban leadership is needed at all levels to achieve value delivery and improvement.
• Understanding – Kanban is an improvement method, and knowing the starting point is foundation.
• Agreement – The commitment to move together toward goals, respecting differences of opinion or approach. It is key to note that this is not management by consensus, but a dynamic co-commitment to improvement.
• Respect – Valuing, understanding, and showing consideration for people.

Agendas

• The Sustainability Agenda looks inward to the organisation. Its goal is to balance demand with capability thus improving the performance. Where demand outstrips capability making work visible and limiting WiP will have a positive impact on the amount of work completed, the time needed to complete work items, and staff morale.
• The Service Orientation Agenda focuses attention external to the organisation on performance and customer satisfaction that meet and exceed customers’ needs and expectations.
• The Survivability Agenda looks into the future and is concerned with staying competitive and adaptive.

Change Management Principles

• Start with what you are doing now
• Agree to purse improvement through evolutionary change
• Encourage acts of leadership at all levels

Service Delivery Principles

• Understand and focus on customer needs and expectations
• Manage the work let people self organise around it
• Evolve policies to improve outcomes

General Practices of Kanban

• Visualise.
• Limit work in progress.
• Manage flow.
• Make policies explicit.
• Implement feedback loops.
• Improve collaboratively, evolve experimentally

Don’t Just Do Something, Stand There!: Ten Principles for Leading Meetings That Matter by Marvin Ross Weisbord, Sandra Janoff & Jack MacNeish
My rating: 3 of 5 stars

We spend a lot of time in meetings so making them more effective will likely greatly improve the performance of bussiness, however people are rarely taught how to run meetings well.

1. Get the whole system in the room
   • Who should be in the meeting
     • The decision makers
     • Data – contracts, time or money
     • Expertise in the issue or field
     • Information about the topic (where the expertise is missing)
     • Affected parties who can speak of the consequences
   • Match the timeframe to the agenda
   • Give people time to express themselves
   • Differentiate then integrate
     • Differentiate into functionally similar groups to clarify their stakes
     • Integrate with the whole group or mixed groups
   • Where it is not possible to get the whole system ensure you have at least three levels and three functions. Providing access to other functions and levels speeds up the whole system.
2. Control What You Can, Let Go What You Can’t
   • Know your role – Do you have content? Are you managing the meeting?
     • No No – You are only observing and commenting
     • Yes No – You are likely an expert who is providing advice
     • No Yes – You are facilitating the meeting
     • Yes Yes – You assume great deal of responsibility for process, content and results.
   • Clarify the purpose yourself
   • Monitor the meeting
     • Seek fight or flight
     • Check for someone being excluded
     • Arrange seating for the style
     • Establish time management norms in breaks
3. Explore the “Whole Elephant”
   • A “go around” – get input from everyone who wants to contribute
   • Use timelines – get all the history from the many peoples views
   • Make a mind map – get all the points out so people have a common view
   • Group flowchart – get all the flows e.g. processes on the table so their is common understanding of the environment
4. Let People Be Responsible
   • Accept everyone is doing their best
   • If people have hidden agendas that is their choice
   • Do less so others will do more
   • Encourage self management
   • Contain your “hot buttons”
   • Encourage dialogue
   • Legitimise opposition in tense meetings
5. Find Common Ground
   • Hold off problem solving
   • Get conflicts into the open and leave them there
   • Focus on the future
   • Back cast from the future
   • Stay with anxiety and ambiguity
   • Depersonalise conflict
6. Master the Art of Subgrouping
   • Ask “anyone else … ?”
   • Differentiate then integrate
   • Listen for integrating statements
7. Make Friends with Anxiety
   • The four rooms of change
     • Contentment
     • Denial
     • Confusion
     • Renewal
8. Get Used to Projections
   • View things in perception not in objects by making yourself the subject. such as It this and that become I or me. e.g. “I’m bored” is “I bore me”.
9. Be a Dependable Authority
   • Everyone reacts to authority – could be good or bad
   • Recognise dependency – going along with everything
   • Recognise counterdependency – not happy with everything
10. Learn to Say No If You Want Yes to Mean Something
    • Be dependable only commit to things which will be done and no to the rest

Nine Lies About Work: A Freethinking Leader’s Guide to the Real World by Marcus Buckingham, Ashley Goodall
My rating: 4 of 5 stars

Lie #1 People care which company they work for

Truth #1 People care which team they’re on

Statistically there is a bigger range of differences between teams which are at the same companies than the average between companies. As such the team you are in and how you feel there is key to your feeling about the company you work for. ADP present eight questions (similar to the ones below) which identify how an employee feels about the team they are in.

1. I am very enthusiastic about the mission of my company.
2. At work, I clearly understand what is expected of me.
3. In my team, I am surrounded by people who share my values.
4. I have the chance to use my strengths every day at work.
5. My teammates have my back.
6. I know I will be recognized when I do excellent work.
7. I have great confidence in my company’s future.
8. In my work, I am always challenged to grow further.

Lie #2 The best plan wins

Truth #2 The best intelligence wins

Planning gives a false sense of security – there is no way that the plan can cover all eventualities and fully reduce risk. The solution is to boost intelligence within the teams by

• Liberating as much information as you possibly can, as fast as possible
• Watch carefully to see which data your people find useful and improve it
• Trust your people to make sense of the data

You should catch up with all of your employees once per week to understand their priorities and how you can help. This should limit the number of people you have working for you – the number you can catch up with weekly.

Lie #3 The best companies cascade goals

Truth #3 The best companies cascade meaning

An example is a sales person – giving them a quota does not mean they will sell any more, instead if they reach their quota they will slow or stop selling so they have more orders for next year. For those who can’t get to their quota they face pressure and fear which can turn to inappropriate and sometimes illegal tactics to meet their goals.

Another challenge is that progress towards a goal is not linear – the example used is you can’t be 68% complete on a marathon as you still might not actually finish in which case you achieved 0 marathons.

Finally it’s impossible to compare people not doing the same task as there is no way to calibrate against each of them or understand their own local markets

Instead cascading meaning is more successful through the expression of values, rituals and stories.

Lie #4 The best people are well-rounded

Truth #4 The best people are spiky

Competencies are impossible to measure, and as such it is impossible to prove or disprove that people who excel in a role have particular skills or competencies. These well rounded people are fictitious – in the real world high performers are unique, distinct and outperform exactly because of their differences.

If you think of a range of top singers – they are a range of diversity and that is why some of them can perform some songs better than others. No footballer is equally good with both feet.

Lie #5 People need feedback

Truth #5 People need attention

Giving negative feedback is 40 times more effective than ignoring people, however positive feedback is 120 times more effective than ignoring people – it helps people be more engaged and more productive.

Negative feedback triggers the flight or flight behaviour, as such negative feedback inhibits learning.

Lie #6 People can reliably rate other people

Truth #6 People can reliably rate their own experience

When rating people the ratings people give are more related to the rater than the recipient (Idiosyncratic Rater Effect). The more complex the rating system the more we revert to our own natural rating pattern. Given that the rating system is more about the rater than the recipient it makes it very concerning that we then use this performance measure to significantly impact the recipient in terms of pay, opportunities etc.

Secondly the rating rate tends to come from a small number of people and they are not all well-informed sufficiently to be able to provide valid data so we have data insufficiency.

• Human beings can never be trained to reliably rate other human beings
• Rating data derived in this way is contaminated because it reveals far more about the rater than it does of the person being rated
• The contaminated data can not be removed by adding more contaminated data

Although we are not reliable to rate other people, people can reliably rate their experience. As such questions like “Do you turn to this team member when you want extraordinary results? this is a question where you look inside yourself – you can’t be right or wrong as this is a feeling the data is humbler and at the same time more reliable (does not fluctuate randomly, does not mean accurate).

Lie #7 People have potential

Truth #7 People have momentum

Potential is a very binary differentiator – in reality individuals are unique and they have a momentum in their own unique direction at their own speed. If we start speaking to people to understand them better then we can also both work with them better, give them more appropriate opportunities, they will enjoy themselves more and ultimately give more.

Lie #8 Work-life balance matters most

Truth #8 Love-in-work matters most

We seem to split work and life from each other – meaning we need to balance them. Research has shown that if you spend more than 20% of your time on activities you love then you feel stronger, perform better and bounce back faster.

Lie #9 Leadership is a thing

Truth #9 We follow spikes

Leading id defined by whether anyone else is following – it is a question of human relationships, namely why would anyone choose to devote his or her energies to and take risk on behalf of someone else. Missing this misses the entire point of leadership.

We follow people who we believe in, it is a feeling we have and no two people can cause us to have the same feeling. So leaders should embrace their own idiosyncrasies and use these as part of their own unique leadership style.

We follow leaders who connect us to a mission we believe in, who clarify what’s expected of us, who surround us with people who define excellence the same way we do, who value us for our strengths, who show us that our teammates will always be there for us, who diligently replay our winning plays, who challenge us to keep getting better, and who give us confidence in the future.

Mastery by Robert Greene
My rating: 3 of 5 stars

This book pulls together some historical examples of learning to gain Mastery by people such a Edison and summarises some of the stages from these.

• Calling – you need to identify what is your passion, not one based on circumstances or one enforced on you by someone else.
• Apprenticeship follows three phases
  • Deep Observation – where you are watching others to understand what to do
  • Practice – trying out your understanding
  • Active – pushing yourself to get feedback from peers or the public
• Strategies for apprenticeships
  • Value learning over money – the best apprenticeships might not pay (well)
  • Keep expanding your horizons – push yourself to look broadly
  • Revert to a feeling of inferiority – be open to new learnings
  • Trust the process – invest the time, gaining skills is quick
  • Move towards resistance and pain – invest the effort, gaining skills is not easy
  • Learn in failure – what can you learn from failure when they happen
  • Combine the “how” and the “what” – seek to understand the how not just what
  • Advance through trial and error – experiment, see what works and what not
• Mentors are key to you being supported through your apprenticeship
  • Choose the mentor according to your needs and inclinations
  • Gaze deep into the mentors mirror – we become overly optimistic with our abilities, you need a grounding to reality
  • Transfigure their ideas – it is not about copying your mentor but absorbing the relevant parts and adapting
  • Create a back-and-forth dynamic – where mentor and mentee learn from each other so that the relationship evolves as the mentee grows their own ideas
• Social intelligence
  • The seven deadly realities – envy, conformism, rigidity, self-obsession, laziness, fightiness and passive aggression
  • Speak through your work – convincing people with quality work not fighting
  • Craft the appropriate persona – so that you can be consistent to listeners
  • Suffer fools gladly – don’t lower yourself to their level or fight them
• The Creative-Active
  • Creative Tasks – choose your task wisely, one which you can obsess about, engage deeply and emotionally commit
  • Creative Strategies – we like to do the same things, it’s easy for us.
    • Negative capabilities – embracing mystery and uncertainty, suspending judgement and admit that we wound up in our own ego and vanity.
    • Allow for serendipity – random external stimuli lead us to association we can not come to on our own.
    • Alternate the mind through “the current” – cycling between speculation and observation/experimentation to dig deeper resulting in a theory which explains something beyond our limited senses.
    • Alter your perspective
      • Search for the “how” not just the “what”
      • Investigate details, don’t just generalise
      • Look into anomalies
      • What is absent, not just what is present
    • Revert to primal forms of intelligence – e.g. drawings and models
  • Creative Breakthrough – sometimes we need some distance from the problem to come back with fresh ideas and perspectives
• Mastery
  • Connect to your environment
  • Play to your strengths
  • Transform yourself through practice
  • Internalise the detail
  • Widen your vision
  • Submit to others – get an inside perspective
  • Synthesize all forms of knowledge