I couldn't cut straight until I bought a June Tailor Shape cutter, but if I didn't have it, I would use my 24 1/2 X 6 1/2 ruler and learn not to let my cutting wander away from the ruler on the far end. I use my cutting mat upside down so there are no lines. I don't find the lines accurate and they are too distracting with all the lines on the rulers. I get a more accurate cut using a normal ruler if I double fold the fabric so I'm only cutting 11" instead of 22".