The Tibloc is a tiny ascender which operates with the use of a small auto-locking carabiner. (Shown here on M18. The M18, M21 and M23 are ideal.) The toothed cam engages the rope when weight is put on the carabiner. The Tibloc is small and compact, and can be quickly installed midline, making it ideal for rescue. Chiefly used by climbers as an emergency ascender. 7/16" (8-11mm) capacity.