You can use 35mm film in a medium format (120) camera.
What you'll need:
I used a Balda Poka, but you can do it just as well with an Agfa Clack, or a TLR like the Yashica-D, or any type of medium format camera. Only a 620 camera like the Kodak Duaflex may not work (much to my chagrin). The 35mm roll is too fat to fit into the camera.
The 120 spool is too big for 35mm film, so to prevent the film from moving left and right, thus producing crooked pictures, wrap some rubber bands on both ends of the spool. Leave just enoug room for the film in the middel.
Take some bits of foam (I took some leftover package material) and cut off some bits of about 3 x 3 cm. The exact size depends on your camera, so just see what works best. Better start too big, you can always cut off some more. Now put the 35mm roll in the camera, and stuff the bits of foam on both sides of it to keep it in place. It should fit in firmly, but make sure the film can still be pulled out easily.
Carefully pull out the end of the film, and wrap it around the 120 spool. A bit of tape might help. Put the spool in the take-up position in the camera.
Now you're almost done. Check if your camera doesn't have one of those little red windows in the back to see the frame number. 120-film has backing paper, but 35mm film does not. If you leave that window unchanged, your fillm will get overexposed. So cover it up with some black tape or a bit of cardboard. I recommentd covering it on the outside of the camera. That way you'll be sure the film won't scrape over it.
