One of the better-known Lean Tools is Kanban. Kanban means signal (card), which is precisely the idea: of using a simple tool that everyone understands to ensure a signal is transmitted. In this case, the call to order raw materials/parts. The kanban indicates that the amount in question needs to be ordered. The card usually also contains the quantity, the order number, the supplier, a bar code, etc.

The Kanban tool is used in everyday practice in many warehouses. On the shelf, a card appears when an article is picked up when a shortage is imminent. In everyday life, we see the same principle being used with cigarette rolling papers, with a colored paper indicating there are only ten papers left, signaling the user to go out and buy new cigarette papers.

In the banking world, the same principle used to be applied to checkbooks: 10 cards before the end, there would be a form that people could use to order a new checkbook. Whenever a cash roll is about to run out in supermarkets, it is indicated with a purple bar on the paper.