The rubbing hole aiguille

This anchor bolt and rubbing hole aiguille is based on the principle of inner protruding structure,by the inner expand bottom-hole,to expand into the structure with a larger bottom-hole and a smaller hole mouth.Expanding the bottom of the anchoring bolt,inserting into the hole,but not sweeling into the hole,the anchoring bolt itself can not bring inflating stress,so it will not bring harm to the wall,therefore it is safe and credible and can endure the stress after installing at once.It is a product which well fit into