I noticed this in Amateur Photographer magazine (25th June 2005) which was a special edition to celebrate 80 years since the first Leica camera and the 80th anniversary of the magazine.
Normally you need to cut the film to make a long leader but this method lets you load the Leica scre cameras without modifying the film.
- Draw the film out of the cassette and insert tip of leader into the takeup spool.
- Lower the cassette and take up spool into the base of the camera.
- As it is part way in, insert a business card between the film and shutter blind, pushing it lightly until there is resistance (the card should be seated against the central part of the shuter housing).
- Start to wind the film on.
- Once you see the film winding freely (by viewing the movement of the rewind knob) remove the card, attach the baseplate and advance a couple of frames.
You can now start using the camera.