I have an 15" X 15" square ruler that is great for making sure my quilt is squared up. I bought it at JoAnn's a few years back. It is made by Omnigrid. I also have a 8 1/2" X 24" Omnigrid that is wonderful for cutting borders, since it is 2 1/2" wider than most rulers. I got it at an Amish quilt shop in PA about 4 years ago (I know, that doesn't help any of you, does it?)