Wikipedia
Film holder
A film holder is a device that holds one or more pieces of photographic film, for insertion into a camera or optical scanning device such as a dedicated film scanner or a flatbed scanner with film scanning capabilities. The widest use of the term refers to a device that holds sheet film for use in large format cameras, but it can also refer to various interchangeable devices in medium format or even 135 film camera systems.
Usage examples of "film holder".
He slipped in a cut-film holder, set the shutter, and hurriedly guessed at the focus.