The foreman of the Grip Department; works with the Gaffer and the Director of Photography in order to delegate the various tasks required for the next series of shots and upcoming scenes.  Usually responsible for the Camera Dolly and its operation (Dolly Grip). 

About

One could equate the Key Grip with the combination of a contractor/foreman one might find on a construction site. Contractor, because of the planning involved in the construction of any device that enables filming be done, and foreman, because of his (or her) hands-on work with the grips under his supervision, whether it be construction or operating the necessary equipment for production (cranes, dollies, tracking, etc.).

Working closely with other factions of the film production team (Production Designer, Director, Cinematographer, Gaffer, etc.), the Key Grip insure that his crew will construct and/or operate anything needed to get "the shot".

History

There are two "schools of thought" as to the origin of the term "grip". One being that during the old days of hand-cranked cameras, the tripods had to be held steady by a tight "grip" so as to get a good shot. Another origin is dates back to the tool bags (slang: grips) carried bags carried by stage technicians during the days of vaudeville.