They make square up rulers. I think mine is 12 or 12 1/2 square. They are fantastic to use. Mine has a 45 degree line on it so I can use it to square HST's evenly. I have bought smaller ones for smaller blocks, but always end up using the large one. Check them out at your LQS or JoAnn's, HL wherever you shop. Mine is old; there may be more on the market.