The unit shelf span (namely length) should not be too long, and the unit shelf depth (namely width) should not be too deep. According to the load capacity of each layer of the unit shelf, it can be divided into light, medium and heavy shelf type shelves, and the laminates are mainly steel laminates. Two kinds of wood laminates. Shelf-type shelves are suitable for storing scattered and light goods, and can be converted into loft-type shelves.