The most common form of active rock protection is the spring-loaded camming device, which climbers simply refer to as a cam. Cams feature three or four aluminum lobes that retract when a spring-loaded trigger is pulled. The device can then be slid into a crack and the lobes expand to fit the rock when the trigger is released.
Passive rock protection has no moving parts, and consists of aluminum or brass wedges that can be securely fit into cracks and pockets. Passive rock pro includes stoppers, nuts, hexes, and tri-cams—all of which are designed for use in specific situations and certain types of rock.