Also called draw slide. a black plastic, metal, or fabric sheet that is inserted into a film holder to protect the film from light.
a lightproof holder for sheet film or a photographic plate.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for dark slide
Moreover, this something evidently had the power of penetrating through the walls of the dark-slide to the plate within.The Romance of War Inventions|Thomas W. Corbin