The decoration of the shopping mall now uses light steel keel ceilings. The surface of the light steel keel is treated with hot galvanizing, which will not rust or deform for a long time. Not a single large-scale place has a wooden keel ceiling. There are also two practical problems. The use of wooden keels is not only bad, but also the cost is not cheap. Now the cost of 50 pairs of light steel keels is the same as that of 3*5 wooden squares, and the light steel keels can return 1-2 meters from the roof. , There are maintenance openings for air-conditioning, fire communication weak current, people can stand on the light steel keel to repair the equipment (at this time, the main keel must be 60 main dragon 60*27*1.2MM), this is impossible for wooden keel. .