Какие функции выполняют люди, скрывающиеся в титрах под титулами Best Boy, Boy Grip?

Best Boy, Boy Grip

AKA: Assistant Chief Lighting Technician, Best Boy Grip, Best Boy Electric. The chief assistant, usually of the gaffer, but more often lately used as a general term for the second in command of a group. This term is likely borrowed from early sailing and whaling crews, as sailors were often employed to set up and work rigging in theatres. There are no «best girls» perse; female chief assistants are also called «Best Boys».

Grip

In the USA, a grip is a person responsible for the adjustment and maintenance of production equipment on the set. Their typical duties include laying dolly tracks or erecting scaffolding. In the UK, grips work exclusively with equipment that the camera is mounted on. Contrast with swing gang, see also key grip.

Key Grip

The chief of a group of grips, often doubling for a construction co-ordinator and a backup for the camera crew. Key grips work closely with the gaffer.