but I didn't until yesterday. I took my 1st quilting class, and I was using one brand of 18" ruler (to cut strips out of my fabrics), and another brand to square it up with. My square was about 1/8" small all around. My seams were right on 1/4", but then the instructor noticed the brands were different. When we tried the same brand square-up ruler as the 18" one, my square was right on the size! Amazing! :roll: :-D