Best Boy Grips
In a film crew there are two kinds of best boy: Best Boy Electric and Best Boy Grip. In the simplest forms, they are assistants to their department heads, the Gaffer and the Key Grip, respectively.
On films with very small crews, the Electric (lighting) department often consists of only a Gaffer and a Best Boy, and the Grip department includes only a Key Grip and a Best Boy. On very large crews these numbers can hit up to 12 or 24 people per department (depending on the situation).
As would be expected, the responsibilities of a Best Boy change depending on the size of the crew. On small shows, they simply place and operate the Grip and Lighting equipment and ensure its continuous and safe operation. On a large show, the Best Boy position might resemble a management position; often they hire the crew and ensure sets are pre-rigged for the Gaffer or Key Grip. The Best Boy also may be responsible for preparing weekly invoices to production departments, ensuring that overtime is paid and handling negotiations with the production team.
Female Best Boys are, as a rule, credited as "Best Boy", but often are called "Best Girl" on-set