I prefer the olfa's and I have collected them over the year so that I have every half inch size from 2" to 6 1/2" and then a couple of large ones for everything else. I prefer them because they have all markings in black and yellow so that one or the other shows up on everything. I use them with a small 6 x 5 cutting mat for most squares .. on a lap desk... the mat moves freely so that I don't have to move the square which I feel is critical to success. I line up the center of the square with the center mark of the ruler.. straighten to make sure it is straight on the side and then trim 2 sides... right and top.... leave square and ruler alone...but rotate the small mat... till it is 180 off from original position. again cut right and top and done... move ONLY on the diagonal after matching the center point.... sliding back and forth will mess up your center.... just match the center...then the diagonal ruler line onto the square and adjust ONLY by sliding up and back on the diagonal..