Chinese steam racks, bamboo or aluminum (jing loong) 
These are layers or tiers of bamboo mesh or aluminum, perforated trays-porous in construction-designed to permit full steam penetration from a large pot underneath.

Water is boiled in the pot. The trays rest on the pot of boiling water and are covered with a bamboo or metal lid during the steaming process. The trays can also be stacked on a wok. The dish containing the food for steaming should be placed on the steam tray. When the water is brought back to a boil, the heat is turned down since rapid boiling does not provide more heat than slow boiling. As for the bamboo steamers, they present a storage problem as they have no handles for hanging. Steamers commonly found in commercial establishments are aluminum for cleaning and sanitation purposes.