How to change films... when rewind is secured
There are those nasty motorized cameras that got a tiny rewind button located in a circular recess, and need a tool to activate it. And still do not deliver such tool (eg. fixed to the handstrap).
The renown Olympus µ-1 is such a camera.
Seemingly one is expected to have a ball-pen, tooth-pick etc. around.
By lack of such tool:
Fold the end of the tongue of the fresh film. Do it in the middle between two perforations, in order not to weaken a perforation.
You gain a sharp corner enabling you to activate that button.
Unfold that crease again before loading that film.