Its unique latch prevents the chain from slipping out of the hook when tension is not applied on the rope. This grab hook will fit either 6 mm (1/4") or 7 mm (5/16") chain. Equipped with 3 links of 7 mm (5/16") chain, it can be attached to any 12 mm (1/2") rope or smaller. Attach the hook to the rope using the bowline knot. The bowline knot provides a secure connection, and can be untied if required.