Almost everyone has used a ruler at some point, whether it was for a school project, measuring something around the house, or drawing a straight line. But even after years of using one, there’s a small detail that’s easy to miss: the hole near the end.

Those holes in rulers aren’t just part of the design. They actually serve a purpose, and the reason they’re there goes back further than most people might expect. Here’s what they’re for, how they were used in the past, and a few other ways they come in handy.

Why Do Some Rulers Have a Hole at One End?

The hole at the end of a ruler is mainly there for storage. It lets people hang the ruler on a hook, nail, or pegboard instead of leaving it in a drawer or on a workbench. This is particularly helpful with longer metal rulers that might not fit in a toolbox.

But the hole has been around for much longer than modern workshops. Years ago, before paper notebooks became common in schools, students practiced writing on small slate boards.…