The metal shelf takes medium-duty or heavy-duty rack as the main part, to use solid steel plate or solid steel checkered plate or perforated plate as the flooring. Single-tier or multi-tier mezzanine can be designed as per requirement, and normally it is 2 or 3 tiers. The height can be up to 5 meters to 9 meters. Stairs, lift platform, hoist, conveyer belt or forklift are used to take goods upstairs. The shelf can take full advantage of valuable warehouse space, because it expands upwards rather than outwards. It usually has a big load capacity with the advantage of low cost and easy installation. Meanwhile, the shelf is suitable for the fields of big height warehouse, little goods, unloading it manually and big storage quantity. Generally, the load capacity of multi-tier mezzanine is 300kg-500kg/sqm. It is widely used for high warehouses with small goods which is operated manually. Mezzanine can make best use of the warehouse space.