Abstract: A fail-safe X-ray film marking system that includes a reusable fastening combination adapted for use in temporarily fastening a marking element to a container that is configured for holding X-ray film. The marking element is at least partially opaque to X-rays, and it is adapted to be positioned on the cassette in such a way that an image of an identifying character of the marking element will be imprinted on the X-ray film (inside the container) after it is exposed to radiation. The fastening combination is formed from X-ray permeable material that will not degrade the quality of an image produced on the subsequently exposed X-ray film; a suitable material for the combination is nylon.The fastening combination preferably includes a relatively large sheet having a pile-like surface comprising a multitude of small, short loops of the kind that can be engaged by a multitude of resilient hooks of the Velcro type.