The Lockjack can completely replace the friction hitches used on climbing lines. It works as both an ascender and descender for self-belay in the moving rope system (MRS). The advantage of the Lockjack is that friction is applied to the rope with a smooth aluminum surface which causes less friction while climbing for an effortless advance, and a smoother and more easily controlled descent. While climbing, the Lockjack tends slack by itself as the weight of rope below the climber pulls the line through the device. The Lockjack is a handy, efficient, yet easy-to-use climbing and descending device for climbing trees. Works with 1/2” rope.