This is what I do.... I cut the first edge off(on the right if you are right handed)...I have the fold on a line of the cutting board. After that, I turn the board around without moving anything. I then put my ruler over the folded fabric and use only the lines on the ruler(not the mat). It comes out perfect every time...no bowing. I hope this makes sense to you. If not I will try to clearify it for you.