Depends. Some safety razors have zero, or almost zero, blade exposure and rely on the ability of the skin to push up past the guard (into the "gap") to reach the blade.
Originally Posted by Crowort
I saw a thread here the other day (I think it was an old resurrected thread) where someone showed close-up pictures of a good selection of safety razors where the varieties of exposure and gap combinations were quite clearly visible. He also had some very plausible explanations on how the different variations affected the shaving characteristics. There were a couple of zero-exposure examples.
Somebody's nuts. I don't know whether it's me or them, but somebody is definitely nuts. I just wished I knew, so I'd know, you know?