The double-deep rack is designed to be the depth of two pallets in terms of the depth of the rack. The rack structure is the same as that of the pallet rack. Generally, the upper layer is equipped with pallet guide rails, which is convenient for forklifts to access goods more quickly. Compared with pallet racks, double-deep racks have a 75-100% increase in storage rate. However, due to the design of the double pallet depth,for a single storage and retrieval position, it is necessary to take out the cargo space on the aisle side before taking the goods of the next depth, which is suitable for the characteristics of small batches and multiple categories of goods.