I use whichever ruler works best for what I want to measure. If I'm going to measure across the width of folder fabric, I either fold it again to make 4 layers and use a 14 x 6 ruler or don't fold it again and use my 6 x 24 ruler. I measure the distance I need, slide my Slidelock ruler against it, making sure everything is still straight, move the ruler and make my cut - usually from the other side of the table as I am right handed. I have both sizes of the Slidelock rulers and use whichever works best with the ruler I am measuring with. I could not cut wide fabrics without them!