Abstract: A film strip cartridge having a film guide channel thru which film may be advanced has a film lock means disposed in the channel to selectively arrest the advancement of the film. The film lock is formed from a resilient wire which has a first end secured to a portion of the cartridge. A nub is formed in the wire intermediate to the first end and the distal end of the wire. The resilient wire urges the nub into one of the perforations formed along the margin of the film to arrest the longitudinal movement of the film and thereby prevent inadvertent film removal.