From the pic it seems that this attachment is used to sew the back of the binding down by sewing it in the ditch in the front after it has been machine sewed first to the back then flipped over so this gadget can finish it? As far as mitering the corners....I think, if I were using this, I would stop sewing near the corner, do the miter, and do that without the attachment, then back with attachment to do just the straight runs????? I think I better go to Nancy's site and see if I can see the demo video....if it does work it would be reat.....when I try to sew that back down by machine in the front ditch, I usually end up "missing" parts of it because I cannot see the back edge and sometimes I just can't "feel" it either.....or if I do sew it down from the back, it does not always lay hidden in the ditch in the front............so back to hand sewing it down............