I took jdiane318 advice and decided to try glue on my broken 15 inch Omnigrid ruler. I bought some Superglue and went ahead. I used clear packing tape on the bottom side to match up the two pieces perfectly (and to catch any run off because I didn't want to glue it to the table). I then used that tape like a hinge to slightly open the crack and ran the Superglue along it. I layed the glued pieces flat on my table to dry overnight. I think it did a pretty good job.