Um, I have a feeling your rulers did not warp. Looks more to me like your cutting table has a dip in it. Try laying your rulers on something you KNOW is flat, like a kitchen counter top and tell me if you still have this "bowing" issue.
Oops, guess I should have read all the posts before replying! LOL It WAS the table. Believe it or not, I could actually make out a dip in the photo.
Last edited by feline fanatic; 10-10-2014 at 04:27 AM.