The Gaffer could also be named "chief lighting technician" and a Best Boy is his next in command. (Gothamist LLC)

The job is not a glamorous one, and usually the only recognition you get for your hard efforts is when the audience sees the term 'Best Boy' in the credits and laughs. (Helium, Inc.)

On films with very small crews, the electric (lighting) department often consists of only a gaffer, a best boy, and a few electricians. The grip department may include only a key grip, a best boy, and a few grips. (Wapedia)