What does a stand-in actor do for an actor?

A stand-in actor is responsible for replicating an actor's movements and positioning on set during rehearsals and lighting setups, allowing the main actor to focus on performance during filming. They typically match the actor's height, build, and sometimes hair or costume to ensure accurate lighting and camera angles. This role requires attention to detail and knowledge of set protocols but does not involve performing in front of the camera during principal shooting.