I square up using a large square ruler 15" or so and 24" long ruler. Place square at a corner and line up long ruler abutted to the square and trim 2 sides of the corner and along the length of the long ruler, move quilt and long ruler up the sides, I stop approxiamtely 24" from the next corner and the place the square on the corner and line up the long ruler with the square and where I stopped on the long edge. sometimes I do "fudge" a bit as sometimes it does not aline 100%. I work my way around using the quilt.