A Foot Ascender is a toothed device which is attached to the climber’s foot by means of a webbing sling. The Foot Ascender’s cam allows the climber to slide the foot up the rope and raise their weight by pushing down and straightening the leg. The Foot Ascender must be removed for moving around the tree and for descent. Something like the Camp Turbo foot uses Rollers and is lockable on long ascents with a carabiner or tool clip. The CT Quickstep is permanently locked to the rope until you unclip the catch. The latest Petzl Pantin is light weight but does not currently have any way of locking to the rope and as such is prone to pop out.