A system includes a inventory pier and a mobile drive unit. The inventory pier includes a first side and a second side. The first side includes defined areas at which inventory holders are designated to be stationed. The inventory pier is operable to receive inventory items from at least one of the inventory holders at least one of the defined areas. The mobile drive unit is operable to transport an order holder along the second side of the inventory pier, wherein the order holder is operable to receive an inventory item from the inventory pier at a location along the second side of the inventory pier.