If you grew up in an old house you probably recognized this slot right away. But you can still see them in some hotels too. These holes were used to dispose of old razor blades. Back before stainless steel blades became common in the 1960s, you could really only get two uses out of a blade (once on each side).
Instead of throwing them in the garbage can, where kids or pets could find them, they would be dropped through the slot into a space behind the wall.
It’s not a bad idea, and some people still use these slots, but if you ever renovate your home you’ll find a pile of razors behind your walls.
Today there are modern versions of this solution that don’t leave a nasty surprise for your contractor, like a “blade bank,” a little piggy bank that stores your used blades.
Does your home still have one of these slots? Maybe you found a pile of razors inside your bathroom wall and always wondered why. Now you know!