The use of two bins for parts or material presentation and inventory control. Parts are withdrawn from the front bin, which is sent to the warehouse and replaced by the rear bin when empty. The bins themselves carry information about part number, source and order quantity. When an empty bin is received from the production floor that information it triggers the reorder or replenishment. When the new parts come in the bin is replaced on the production floor behind the other bin.
"Bins" can be commercially available plastic or metal bins, cardboard boxes, pallets or carts... anything that accommodates the appropriate amount of parts or material and carries the reorder information.