I used a lightweight pellon/'wonderunder"/stich-witchery......I don't know what you call it!!! It's an iron-on fuseable interfacing (?). You can tell what an expert I am!!! I won't use the lightweight again...didn't seem to stick as well as the medium weight that I used on a tshirt quilt for my son a few years earlier. I will get the medium again for the one I'm in the process of putting together. Thanks for asking!