With my 3.5e came a plate adapter back with two cut sheet film holders. I now am trying to figure out how exactly they are to be used. It seems I've got on part more than shown in the manual. From back to fore these are: the back of the holder with the turning key (attached to 1) the carrier that comes forward when the key is turned a black plate the size of a film sheet that slides sideways in and out the carrier (as the sheets do) the black slide that covers the film What is the black slide (#3) for? The illustration in the manual just shows the carrier behind the film.