I couldn't believe it when I first saw this 'shortcut'. Where was this when I was replacing all those zippers on kid's sweatshirts?!? Since then I have used it on sweatshirts, jackets, a purse and a sleeping bag. The trick is to cut out the old zipper as close to the stitch line as possible and then using your zipper foot, sew the new zipper on top of the old tape as close to the first stitch line as you can. It simply looks like a double topstitching line. And it is so fast!