Originally my daughter wanted me to sew her bag using oil cloth, but I wasn't comfortable with that. Since I knew she wanted it waterproof on the inside, I looked at JoAnn's and found the laminate iron-on. It comes in a narrow (maybe 24 inches) and by the yard in the interfacing section. You cut it to size and iron it on with a warm iron. It adhered well. It is supposedly machine washable on a gentle cycle, but I told her I would hand wash it to be safe.