US Patent 9346620 System and method for order fulfillment

A system includes a first mobile drive unit and a second mobile drive unit. The system also includes a first inventory holder, a second inventory holder, and a third inventory holder. An inventory station includes a first location and a second location and the inventory station operable to receive a first inventory item from the first inventory holder at the first location. The first inventory holder is transported by the first mobile drive unit. The inventory station is also operable to receive a second inventory item from the second inventory holder at the first location. The second inventory holder is transported by the second mobile drive unit. The inventory station is also operable to receive a third inventory item from the third inventory holder at the second location. The third inventory holder is fixed at the second location while the inventory station receives the first inventory item and the second inventory item.