I wish I could help...I have never been properly taught to rotary cut, but just do the best I can from what I see/ read online. I know they are off at times and I have no clue how someone squares up big pieces of fabric/ quilts!! I believe this is why I have yet to do anything but a rag quilt, because I know it will be a disaster and the disappointment will be too much. I hate when I can't do something perfectly-Grrr