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!