Best Boy
1. In a film crew there are two kinds of best boy: best boy electric and best boy grip. They are assistants to their department heads, the gaffer and the key grip, respectively. Best boys are responsible for the daily running of the lighting or grip department. Their many responsibilities include the 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 (where relevant), and serving as the day-to-day representative of the department with the unit production manager and coordinator of the film.
Source: Wikipedia