I have one of those! I use it to mark across the quilt where I want to FM a simple curve, etc. It gives you correct spacing without having to do major math! I have used it several times in quilting, but I already owned it (for buttonholes many years ago) so don't know if it would be worth buying it now. I love gadgets, but sometimes forget I have one that would help in that particular instance, and forge ahead without it! lol