I sold this machine a few years ago, but my memory was that there was a lever that flipped a rubber over to make contact and run along the edge of the balance wheel.
The "new technology" of multi blade razorsactually pulls your hair up and then cuts it. This can cause ingrown hairs. Straight razors just shave the hair off. The new technology" razors are designed to be thrown away, so that you will keep buying more fore the rest of your life!
I sold this machine a few years ago, but my memory was that there was a lever that flipped a rubber over to make contact and run along the edge of the balance wheel.