The threaded shackle locks the lock door in the closed state when the screw is tightened, avoiding the risk of accidental knocking. Ordinary shackle without threaded device, light weight, convenient operation, can be used for temporary protection points. If ordinary fishing ring is used for fixed protection, it must follow double shackle and the principle of using the door. c The longitudinal tensile force of the shackle is greater than Lateral tensile force, the longitudinal tensile force will decrease when the hook and loop door is opened. The hook and loop door is the weakest link and cannot be directly stressed. The correct way to use it is to keep the hook and loop door closed and longitudinally stressed. Avoid high-altitude drops or hard objects that cause internal cracks to cause the hook and loop to become obsolete. In the case of a climber, such as a climbing, the climber should directly connect the main rope to the seat belt, and the hook and loop should not be used as an intermediate link. You should use a UIAA or CE certified hook and loop, not using a hook and loop of unknown origin.