I broke my 15 inch square in half a while back. Someone on QB suggested Superglue. It was a clean break so I carefully lined up the 2 pieces wrong side up on my table. When I had them perfect, I ran a long piece of clear tape along the crack, I then flipped the ruler back over and brought the ruler over to the table edge. I carefully used the tape on the back as a hinge and opened up the crack and ran a bead of the superglue along the edge. I quickly slid the whole ruler back up on the table and held it in place for a few minutes making sure all the edges by the break were still perfect(they must be aligned perfectly so the cutter doesn't snag) I put a book on either side of the glue (away from the crack) and left it overnight. My ruler is still going strong and it's been months of regular use.