Work that hasn’t been deployed, shipped, or otherwise delivered to a customer has no real value. Value is only realized when the work is available for use by the customer. The naive assumption is that the more work in progress there is, the more work will get to ‘Done’. Yet evidence is to the contrary. More work in progress results in less work done. (See The Impact of Agile Quantified for more).
The use of a Kanban board is a simple way to help limit Work in Progress by having a column that visually displays the work that exists in that state, and setting a maximum limit of the quantity. The idea is that we shouldn’t start new work before the existing work gets to done. Once a column has a WIP limit and the column fills up, then we’re forced to move downstream to help get the most downstream work to truly done.
Over time, teams often reduce their WIP limit to improve flow. Each reduction will challenge the team to cross-skill and collaborate more.