I start the grid on the edge of the middle quilt line and go edge to edge. Then I finish one side, turn and start on the other side. Same with the opposite grid lines. I use a Straight Edge ruler for marking my lines (bought at Lowe's) it's 2 1/2 inch wide metal ruler and comes in various sizes. I have the 4 ft and 6 ft. The longest one is only $12. My smallest quilt ruler cost that much. LOL