Originally Posted by
crocee
I use the lines on the mat because as Sharon Schambler says, they don't move. Sometimes no matter how careful we are that ruler will mover ever so slightly and we get a crooked cut. By keeping everything lined up with the lines on the mat you can be assured your cut is straight, well unless your mat is twisted and warped.
That makes no sense to me. Even if you're using the lines on your mat you're still using the ruler itself to cut against so you still have the possibility of it moving during the actual cutting.