A device for coupling a strip of photographic paper to a conveyor belt in a developing machine comprises a rod to which the paper strip is attached. The rod has a hook-shaped end portion for gripping one lateral edge of the flat conveyor belt. Slidably mounted on the rod is a slide member formed with an obliquely projecting lip for gripping the opposite lateral edge of the belt. A spring-biased toggle linkage is effective to retain the slide member in the engaged position, in which the belt is resiliently compressed between the hook-shaped end portion of the rod and the lip of the slide member.