M12 male thread Expansion screw hook anchor bolt with flat washer and hex nut. Open hook bolts suitable for secure and reliable fixing of items and fixtures to concrete, brick, walls and any solid surface. Installation methods: Select a chopping bit with the same diameter as expansion screw casing, and install it on the electric drill for punching. The depth of the hole should be equal to the length of the bolt. Then insert the expansion bolt set into the hole. Remember: Do not screw off the nut and prevent the bolt from falling into the hole when the drill is too deep. Tighten the nut for 2 to 3 buckles and unscrew the nut when expansion bolt si very tight without any looseness. Then the fixed items are mounted with perforated fixed part and installed aiming at bolt. The gasket or spring washer outside is used to screw the nut tightly.