The Wedge is the Simplest of Tools

The wedge is the simplest of tools. A wedge has a flat end and a pointy end. A wedge converts a blunt, general force into a sharp, narrowly focused force. A wedge is very effective at separating things, breaking things apart or dividing them into portions. I learned to respect and value the wedge years ago while splitting logs for our fireplace with my father. Even the heaviest, hardest and most intimidating logs could not resist a few hits on a well placed wedge.

This simple machine called the wedge is useful both practically and metaphorically in terms of kaizen.One definition of kaizen is to “break apart, remove the bad, and put back together” and so we can view human insight and creativity as the wedge that breaks apart and separates work into its components of value added, non value added and waste.

The sharper the wedge (more focused effort) and the longer the edge of the wedge (deeper our observation) the more effectively we can analyze processes and get the waste out. In fact this is called mechanical advantage (MA) and can be mathematically expressed as:

MA = S / T
With S being the slope or long edge of the wedge and T being the thickness of the flat end of the wedge, which of course affects the angle of the sharp end.
A wedge can also be used to hold objects in place. The wedge metaphorically plays an important role in sustaining improvements and making sure lean implementations are long-lasting.


We can think of the wedge as documented standards, ongoing training of people to these standards, the practice of daily / weekly / monthly “go see” audits of these standards, and rapid response problem solving to amend these standards. The PDCA wheel in the above picture is the Plan Do Check Act continuous improvement cycle, supported by the wedge of sustaining the results. When you forget the results, the PDCA ball is liable to roll back down the slope.

Another practical use of the wedge is to keep doors open. During a kaizen event or in a lean training session a meeting room can get hot and stuffy, so open windows and wedges in doorways come in handy. Metaphorically, we need wedges to “keep the door open” to various options and possibilities, as well as to keep the door open on the lean transformation itself in the face of prevailing winds. Such a wedge might be a minor success that keeps management interested in trying other lean projects, exploring alternative process options in parallel through so-called “moonshining” or other experimentation, or a very senior manager strategically positioned in the lean steering committee to keep the door from shutting of it’s own accord (normal backsliding).

So the next time you kick a wedge under a door or pound it into a log, whisper a quiet word of thanks that such an effective tool was invented so long ago.