I have also used it to rescue a film after a camera broke mid roll.

Most recent case was a Pentax ME-F which appeared to work perfectly (I fired the shutter with no film about seventy times with no problems) then developed the non-cocking shutter problem about six frames into the first roll. As all the M series bodies (apart from the MX) use the same spacing between cartridge, shutter and winding drum I was able to swap it into an ME, fire the shutter with the lens cap on to get past the already exposed frames, then shoot the rest of the roll as normal. Aside from three or four frames which the ME F had spoiled while expiring the rest of the roll was saved.