You know, you can always draw a line down the center on the diagonal and then sew 1/4" on each side of it and then cut on the line and you'll get the same results. I have a doo-hickey that is 1/2" wide with slots in the middle and I draw on either side and inside the slots and then I sew down the drawn lines and cut where I drew on the slots. I don't know where on earth I bought it, but I think that is what you are looking for. I usually don't use it. I do it the way I told you.