The metal pull tab broke off of the locking zip slider on my kid's school jacket, which made zipping and unzipping a bit tricky for small hands.  Replacing the whole slider seemed difficult.  Printing something out that could be clipped on to the slider was a much easier option!  

It fits into the slider pretty securely.  I tested it with some force and was unable to make it come off, but time will tell how it lasts.