Expansion screw fixation principle: Expansion screw fixation is the use of cascade slope to promote the expansion of friction grip, to achieve a fixed effect. One screw thread, a vertebral degree. Outside the package wall, wall sleeve half a number of incisions, threw them into the wall Thih well together, and then lock the nut, the nut pull the screw out, pull the vertebral level into the metal cylinder, metal cylinder Was opened up, so firmly fixed on the wall, generally used for fencing, awnings, air conditioners and other cement, brick and other materials on the fastening. However, its fixing is not very reliable, if the load is greater vibration, may occur loose, it is not recommended for the installation of ceiling fans.The principle of expansion bolts is to hit the expansion bolts on the ground or the hole in the wall, with a wrench to tighten the nuts on the expansion bolts, bolts go out, while the outside of the metal sleeve does not move, so the big bolt under the put Metal sleeve opened up to make it full of holes, this time, expansion bolts can not pumped out.Color zinc plating treatment: humid environment, anti-rust.Carbon steel: strength comparable to steel hardness