Do you have problems that may be caused by the way you cut your fabric? If not do it the way you want! I use the lines on the ruler as much as possible because cutting on the same line on my mat can cause problems to my older mats. putting cut ridges in or even removing some of the lines by cutting away small amounts every time you cut. (these are not self healing mats, I've never had one of those) just remember to keep the fabric you want to use under your ruler. If you are cutting left handed keep non used portion of fabric to your left. line up correct line on ruler with the raw edge, an make your cut like always. Just do what works for you and enjoy the process!