system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does a leather strap sharpen a razor?

In movies and TV you always see people running a straight razor back and forth on a leather strap. How can this possibly sharpen a metal blade?
gpt
> How can this possibly sharpen a metal blade?

It doesn't sharpen it, it hones the blade.

When you sharpen a blade the edge is made very thin. It is so thin that it is flexible, and can easily be curled over by use or even accidentally while sharpening. This makes what would otherwise be a sharp blade a bit blunt. By running the blade backwards against the leather strap the curled edge can be straightened back out, returning the blade to peak sharpness.