Suitable to use for cement concrete materials Fixation principle: The expansion screw is by using the wedge angle to prompt expansion and creates friction, to reach the fixed effect Need to use a 12mm diameter drill bit for drilling holes, the drilling depth should be great than or equal to 6 cm Installation: First, insert the expansion screw into the soil-cement admixture, hard twist the closed hook until can't twist it anymore Second, screw the nut with wrench until it fixed Finally, tightening the closed hook again.