A spring-loaded camming device
) is a device used to secure a climbing rope
to the rock
. It consists of a stem with an axle at one end holding four spiral-shaped spring-loaded cam
s. When placing an SLCD, the climber
pulls a mechanism to retract the cams, places it in a crack with the stem pointing down, and relases the mechanism, allowing the cams to spring back against the rock. When the SLCD is pulled downward (say, because of a fall), the spiral-shaped cams are forced harder against the rock, making it more secure.
SLCDs are much easier to use than monolithic protection such as tapered wedges and hexes. They can adapt to the rock and hold themselves in place, making them usable in more situations. They have allowed climbers to climb many routes that were too dangerous to climb using other types of protection.
Ray Jardine is usually credited with having invented the first usable SLCD, which he called the Friend. It was marketed by Wild Country. Today, other manufacturers of SLCDs are Metolius and Black Diamond.