The Quilters Slidelock is not suppose to be a ruler. You put it on top of a ruler. It holds the ruler perfectly in place and most important it keeps your fingers away from the rotary blade. To me, it's not a matter of if I have a rotary accident but when I have one. I bought it for the safety factor and use it because it works great. I don't cut without it. In my opinion the cost is nothing compared to the distress of a sliced finger, ER visit, and meds. It is one of my must have tools, no exceptions.