This binding ruler is designed to allow you to attach a 2.5" binding strip while the quilt is still on the longarm. A groove located on the underside of the ruler, locks the binding in place and will allow you to precisely attach a binding while it is on the long arm with a perfect quarter inch seam. You will not even need pins! You will be able to create accurate diagonal stitch offs in the corners to create a beautiful miter and continue down the sides of your quilt. If you are a hobby longarmer, or in it for a business, this will make adding your bindings a breeze.