Kanban, which means signboard in Japanese, is a workflow management system. The most widely used implementation is Kanban cards. A Kanban card is a colored card which is attached to the container used to move the output of one process to the next process. When the next process consumes that material, the kanban is returned to the producer process, authorizing the producer process to make the next container load of output. The aim is to make sure each part of the factory stocks only the inventory that is needed, no more, no less. This eliminates ‘stock outs’ and reduces inventory carrying costs.