The kanban card is the agent that drives the level-loaded production cell. Kanban cards can be made from readily available paper stock materials. When the kanban cards are placed on the heijunka board following defined scheduling rules, these become the level-loaded schedule for the shop. For these reasons, the kanban cards control both inventory levels and shop schedules. There are two classifications of kanban cards: manufacturing kanbans and purchasing kanbans. Purchasing kanbans are only slotted on the purchasing heijunka, and the manufactured kanbans are only slotted on the manufacturing heijunka. The production control person or scheduler makes rounds of the factory floor and retrieves the kanbans multiple times per day and brings them to his work area next to the scheduling heijunka boards. The standard heijunka boards have at least a two-week, rolling window, columns labeled by weekday name only, for scheduling.