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.