In SRT climbing, a single static rope is attached to the climber's harness and anchored to the tree. The climber ascends and descends the tree using mechanical ascenders, such as a rope wrench or a mechanical friction device, which grip the static rope. The climber relies on mechanical ascenders to ascend the static rope. These devices grip the rope as the climber applies upward force and slide easily when the climber applies downward force. SRT climbing often requires specific mechanical ascenders or friction devices.