Production kanban, which translates to "sign" or "signboard" in Japanese, instructs an upstream process on the kind and number of goods to produce for a downstream process. In a pull system, a kanban is a signalling tool that provides approval and instructions for the manufacture or withdrawal (conveyance) of products. The conveyance used by the downstream process is referred to as the "withdrawal." The assembly process and the client, the assembly process and the supplier process, and the supplier process and the vendor all benefit from kanban. The Toyota production system is founded on zero inventory, but because there are natural interruptions in flow as raw materials are transformed into completed goods and supplied to customers, some required inventory must be included. The Toyota kanban system is frequently the next best option when clean flow is impossible due to processes are too far apart or the cycle times to complete the operations vary greatly.