When hiring background actors, casting directors generally seek those with a specific "look," such as "high school students" or "affluent senior citizens," consistent with the context of the film.
Casting directors may also look for background actors with a special skill for the scene, such as rollerblading, or dancing. A background actor is often expected to bring his or her own wardrobe to the set, although there are also "fittings" for a specific scene or period. A casting director may favor the one who already has the required costume or prop, such as a police uniform, or a musical instrument. On other occasions, where a costume has already been prepared (for example, to fit another actor who is now unavailable), a background actor may be selected as a "costume double" simply because they are the right size to fit it. On smaller productions or student films, background actors may be hired en masse with little formality.