I have one that the corner chipped on, and instead of cutting the top off, we just made the corner a neater angle (hardware store is the best place, as mentioned) so we could keep the inches on the side. Now my MIL has a square ruler with an angled corner for other projects.

I'm a little anal and had to get a new one instead, but she was smart and made it better than before!

I've broken a couple of them over the years.. gotten a couple of new ones.. but a chipped corner doesn't bother me.

I have a ruler that the corner broke off and I put it back using clear packing tape. It's holding up fine and it's been several years.