Cam: also know as an "active cam" as opposed to "passive devices" such as nuts or chocks. A mechanical device, first invented by Charles Jardine, that is inserted into a crack in the rock and substitutes for a piton as a way of attaching a rope to the cliff face. This is call "protection" and climbers use it to protect against a fall. They can also be used for direct aid.

For a scientific analysis of how they work, click here.