Push Back Systems operate by placing pallets on a series of nesting carts fed forward by gravity on structural steel rails. Pallets are loaded from the front, pushing the pallet behind it back one position. When the picking pallet is empty, the pallet is removed from the front and the rear pallets automatically index forward into the front picking pallet location. Pallets can be stored 2-5 pallets deep, all loading from a single aisle. This greatly reduces the number of aisles in the warehouse, freeing up valuable space for increased storage density.