I haven't read all of the notes, but when placing the ruler on the material you have to first see that the selvedge is straight with the opposite side, then line up a straight line on the ruler at the fold, and without moving the ruler, cut across the material to the other side... then don't move the material but carefully turn the cutting mat around so you can then cut the strips... with every strip y ou cut you have to line the ruler up with the previous long cutting edge and ALSO the fold line otherwise you will get an elbow in the material... if that happens, then recut again (square up) and start all over again... just make sure that you don't move the material at any stage... if the material is long I just fold it and lay the excess on the mat, turn the mat around, then carefully unfold the excess , then cut strips...