What does a dolly grip and a best boy do in filmmaking?

Question

After spending the whole morning watching movies, I noticed these on the credits. What do they do?

Answer 1

A "dolly grip" holds the cables for the camera as it's moving back and forth to keep them from getting in the way so the cameraman doesn't trip on them.

"Best boys" are responsible for the daily running of the lighting or grip department. This encompasses many responsibilities including hiring and scheduling of crew, the ordering and returning of lighting or grip equipment, workplace safety, timecards, expendables, loading production trucks, planning and implementing the lighting or rigging of locations and/or sound stages, coordinating rigging crews and additional photography units (if applicable), handling relations with the other production departments, overseeing the application of union rules (if applicable), and serving as the main daily representative of the department with the unit production manager and coordinator of the film.