AT HEIGHT RP280ST Rope Wrench Zk-2 with Stiff TetherSinging Tree Rope Wrench (STRW) is used to create a bend in the rope, above the climbers hitch. With the addition of a stiff tether, the STRW created a 'contained double rope system', on a single line of rope. This contained double rope system travels with the climber as they move around the tree, allowing a consistent level of friction on the hitch, which is impossible to achieve in double rope climbing.