I too mark mine, I thought once to try it without marking, spent more time ripping than I would have if I would have marked in the first place. There is a little tool, if you will, its just plastic that you tape to your machine that has a line that runs from your needle towards you that when you sew you are supposed to run the corner of your square up towards the needle to keep you straight(if that makes sensehow I said it)I tried marking my machine with tape, but have better luck with marking.