In the TPS (Toyota Production System), a unique production control method called the "kanban system" plays an integral role. The kanban system has also been called the "Supermarket method" because the idea behind it was borrowed from supermarkets. Such mass merchandizing stores use product control cards upon which product-related information, such as a product's name, code and storage location, are entered. Because Toyota employed kanban signs for use in their production processes, the method came to be called the "kanban system." At Toyota, when a process refers to a preceding process to retrieve parts, it uses a kanban to communicate which parts have been used.