Carabiner
HMS: A special kind of carabiner is often used in rock climbing. HMS = HeMi Spherical. i.e. offset, or curved to one side.  HMS is also considered short for the German word, "Halbmastwurfsicherung", a knot which is called the Munter Hitch in English. The special offset shape of the HMS carabiner allows a climber to use the Munter Hitch for belaying without the rope getting stuck or jammed.