The ad says they cut 200 squares in two hours. I can cut that many without that ruler; just a plain ruler. And in less than two hours. I prepare both ends of the fabric folded in half, layer them nice and straight, maybe pin that a few inches in, and cut about 4 strips from that end, but don't move them. Let them lay as they are cut. Pull the uncut fabric away a little, then put the ruler the other way and cut 16 squares with one cut. Four strips of four layers.
With 42 in. fabric, you get 10 squares from a strip, times 4 equals 40 squares with that set. If you did five strips you would have your 200 squares by doing this four times. Half an hour!