The Sm'D Screw Lock from Petzl is a D-shaped, versatile, compact and therefore light locking carabiner that can be opened even in difficult conditions, such as mud or ice. As long as the carabiners is not locked, a red indicator is visible. The D-shape allows versatility in activity, for example with a belay system or pulley, and the H-shaped cross-section saves weight and makes it easier to handle with gloves.