Others place them such that they can be easily read when viewed on a light table or before being placed in a viewer. The scheme adopted needs to be consistent throughout the collection and needs to accommodate the major use style of the patrons. Libraries which do not wish to or cannot modify the mounting may place slides in labeled sleeves or pouches made of various materials of varying opacity but this impedes access to the collection and is not considered desirable. Labels do add measurable thickness to slides and this can be significant in large collections. Where space is at a premium and integrity of the original mount need not be maintained, libraries may permit direct notation on the mounts as an alternative to labeling.
Mounts wear out after time and are subject to damage during viewing and projection.
Repairs are not generally possible or even desirable. The library should be prepared with a stock of replacement mountings and the tools and materials necessary to remount film. Plastic mounts are preferable because they are thinner and stronger than the standard paper mounts and are acid-free. Lens brushes and cloths, pressurized air and other appropriate cleaning materials should be available to clean slides before they are returned to storage after use.