stand-in
noun
°A stand-in is an acting term that refers to a person of similar size and shape to an actor that "stands-in" for the actor during the lengthy process that is involved in setting up a shot. This term is not to be confused with a double. The stand-in does not appear in the film.
"They used a stand-in to set up the lighting so that the actor did not have to be there during the lengthy process."