Epson Perfection V500 - Manual (Page 44)

Note:
Hold the edge of the film gently when touching the film; otherwise you may
damage the film.
Do not cover any of the small holes in the film holder or the slot on the side
of the film holder; otherwise, the scanner may have trouble recognizing
which film holder you are using.
Close the cover over the film and press it down until it clicks. Then press down on all the
edges of the cover to secure it.
Make sure the film is placed as shown.