I start in a corner for diagonal lines and I use an old pizza cutter and a ruler to mark my lines. I am lazy and hate to remove the painters tape. I was using a Hera marker and it kind of drags on a long line I thought that it would be nice if it rolled like my chalk marker (which is more or less worn out)Then the lightbulb went on. My pizza cutter is so dull it would not even cut pizza anymore so I tried it. I did test it first to be sure.