The supermarket is a tool of the pull system that helps signal demand for the product. In a supermarket, a fixed amount of raw material, work in process, or finished material is kept as a buffer to schedule variability or an incapable process. A supermarket is typically located at the end of a production line (or the entrance of a u-shaped flow line).
In lean manufacturing terms, a supermarket is a tightly managed amount of inventory within the value stream to allow for a pull system. Supermarkets, often called inventory buffers, can contain either finished items or work-in-process. They are used to handle finished goods inventories being replenished from a continuous flow pacemaker process, between a continuous flow process and other manufacturing processes that are shared by other value streams and for incoming parts and material being pulled from supplier locations.