In American and Canadian film-making, the key grip is the chief grip on the set. Like a foreman, the key grip directs a crew of grips, some with specialized skills such as dolly grips, crane operators, camera car operators, etc.
Additionally, the key grip is often the safety monitor of the film set, responsible for safety of all personnel in the presence of theatrical ballistics, pyrotechnics, stunts, and any other potentially dangerous situations and devices operated by other departments.
In the U.S. and Canada, grips are lighting and rigging technicians in the film and video industries. They make up their own department on a film set and are led by a key grip. Grips have two main functions. The first is to work closely with the camera department, especially if the camera is mounted to a dolly, crane or other unusual position. Some grips may specialize in operating camera dollies or camera cranes. The second is to work closely with the electrical department to put in the lighting set-ups necessary for a shot.
In the U.K. and Australia, grips do not get involved at all in lighting. In the so-called "British System", adopted throughout Europe and the British Commonwealth, a grip is solely responsible for camera mounting and support.
The term 'grip' dates back to the early era of the circus. It carried on from there to vaudeville and on to today's film sound stages and sets. Some have suggested the name comes from the 1930s-40s slang term for a tool bag or "grip" that these technicians use to carry their tools to work.