I also should mention that Movie negative will almost always have Bell and Howell perforations, they are rounded at the ends, Most still film has Kodak Standard perforations wiich have rounded corners and straight sides on all four sides. That can help separate out some industrial or special purpose film.

The Bell and Howel perfs actually have a sharp corner where the end meets the sides, which makes the film slightly weaker, but the rest of the design works better in movie printing equipment.