A "stand-in" is a person who temporarily takes the place of another, often in film, television, or theater productions. They are used during rehearsals or for specific scenes to help with lighting, camera angles, or blocking, allowing the main actor to prepare or rest. Stand-ins typically resemble the main actors in height, build, and sometimes appearance, ensuring that the visual continuity remains consistent. This role is essential for the smooth operation of a production, as it helps save time and resources while maintaining the quality of the final product.