The idea of using a lean production for competitive advantage pdf task board with index cards or sticky notes is as old as Agile itself. The cards represent work items that are in the current scope of work. Names can be associated with the cards to indicate who’s working on what.
Of course, a variety of electronic tools exist that perform these functions, but the simple task board represents a couple of lean principles that I find very valuable, simple technology and visual control. The utility of such a simple method of workflow management is that it is easy to manage, and more importantly, it is easy to change. A problem with the basic index-card task board is that there is nothing to prevent you from accumulating a big pile of work in process. Time-boxing, by its nature, sets a bound on how much WIP that can be, but it can still allow much more than would be desirable.
If a kanban is a token that represents a work request, and our task board can still get out of control, then what is the problem here? The problem is that a kanban is more than just a work request on a card, and putting sticky notes on a whiteboard is not enough to implement a pull system. In a modern economy, the production and distribution of scarce goods and services are regulated by a system of money and prices. Money can be represented by currency notes, which have little intrinsic value, but that by agreement, can be exchanged for real goods and services. If a currency note can be exchanged for an object of real value, then there must be some way to enforce the scarcity of the notes in a way that corresponds to the scarcity of real value in the economy. In practice, some kind of institution must enforce this scarcity.
A kanban represents a portion of the productive capacity of some closed internal economy. It is a medium of exchange for the goods and services provided by the operations of a system of productive resources. The supply of kanban in circulation is controlled by some regulatory function that enforces its value. That is, a kanban is a kind of private currency and the shop floor manager is the bank that issues it, for the purpose of economic calculation. If you carry the currency analogy further, then you might say that kanban is not about the cards at all. Just like money is not about the bills.