I did that with a 12" square ruler, as long as you glue it accurately it works fine.

The total fixer upper. Duct tape. LOL

This is probably a better idea than glue since it will cause less distortion in your measurements.

I would even if the break to eliminate any sharp, or ragged edges and be glad I now have TWO rulers! ( and order a new one to replace the broken one, since you did get your money back.)

Years ago my grandson sat on my 6"x 24" ruler and it broke I bought a new one and then continued to use the broken ones where one half was 6"x 10" and the other was 6"x 14" I loved my short rulers and use them always.

I repaired a ruler I loved with super glue.. but what I did was, first I taped the back side of the ruler by laying the tape sticky side up and putting one half down on the tape.. then I aligned the second half perfectly with the first half.. it's important that you have every line and edge perfectly aligned or you'll never like it again.. Once the second half was stuck exactly where it needed to be I ran a line of glue along the crack.. it will easily go down and glue the pieces solidly together.. hold it tightly together for a bit of time and then let it sit flat overnight.. My ruler has been as good as new. I use LOCTITE Super Glue Proffessional. This glue repairs anything!

I'm thinking epoxy glue. You can look it up on Amazon.

So glad you asked this question - good knowledge just in case, or better yet, when I brake one of my rulers.

Since it cost you nothing - very honest seller - buy a new one.

I broke the corner off my 6 by 24 ruler and here is how I repaired it. First, I matched the two pieces as carefully as I could and taped them on the back side with extra strength clear packing tape. Then, from the front side I glued it with crazy glue or some kind of glue that filled in the crack. I've been using it this way for well over a year and it seems to be holding up fine. Hope this helps.