Expansion screw is widely used in various decoration occasions because of its small borehole, large pulling force and flat exposure after use. If it is not used, it can be demolished at will to keep the wall level. Expansion screw is generally referred to as metal expansion screw. The fixing of expansion screw is to use wedge inclination to promote expansion to produce friction grip force and achieve fixed effect. The screw is threaded at one end and tapered at the other. A sheet iron (some steel tubes) is wrapped outside. Half of the sheet iron cylinder (steel tube) has a number of incisions. They are inserted into the hole punched in the wall together. Then the nut is locked. The nut pulls the screw outward, and the taper is pulled into the sheet iron cylinder. The sheet iron cylinder is raised and tightly fixed on the wall. It is generally used for protective railings, awnings and awnings. Tightening of air conditioning on cement, brick and other materials.