Another thing you can do is get some tape and place it on the bottom of the ruler along the line you want to cut. You can easily see the edge of the tape and there's even less of a possibility of a cutting error because you aren't constantly looking for a specific measurement. Put it on the bottom of the ruler for precision if you put it on the top, you may get different size cuts when looking thru the thickness of the ruler. I've used different colors of electrical tape & blue printer's tape. Just remove it immediately to avoid any sticky residue.