Old homes are full of character—and design quirks like phone niches and card table doors. If there’s a mysterious slot (or two) in the back of your medicine cabinet, then your bathroom wall may be filled with something unexpected.

Houses built in the early to mid-1900s with an original medicine cabinet in the bathroom may have an unassuming little slot on the back wall. Once upon a time, these slots served a surprising purpose: to dispose of razor blades! Here’s a brief history on your medicine cabinet razor slot.

Why do medicine cabinets have a razor slot?

Safety razors for men were invented in the early 1900s. The first one was released in 1903 by Gillette, the same razor brand that many people use today!

Designed to allow men to shave at home instead of visiting a barber shop, these at-home razors had replaceable blades that needed to be changed periodically. However, this left households with piles of used razor blades to dispose of, and they couldn’t be tossed into the trash, as the used blades were technically a biohazard. So what did they do? Drop the blades into their walls!

To create a “safe” way to dispose of used razor blades, medicine cabinets were designed with a razor-sized slot in the back. The cabinet was installed into the bathroom wall between two studs, and when men needed a new razor blade, they would drop the used one into the empty area within the wall. Out of sight, out of mind! There are lots of quirks you may find in historic homes, but this is definitely one that might catch you off guard.

This practice tapered off in the ’70s when fully disposable razors became the norm, but many of the cabinets—and the piles of razors in the wall—are still around today.

Is it dangerous?

Having walls filled with razor blades does sound a bit ominous, but there’s no real danger so long as your wall remains intact. The blades aren’t going anywhere, as they’re trapped between the studs within the wall.

However, if you decide to renovate and open up the wall, you’ll want to use caution, especially in the area behind the medicine cabinet. Wear protective gear while working in the area, and if you find a cache of old blades, you may want to purchase a blade bank to dispose of them safely.