This is an industrial type attachment, used in conjunction with a narrow right coverstitch. The double fold bias binders fold the binding fabric from the top and bottom so that it encases the main fabric on both sides. It works well to bind woven fabrics as well as knit fabrics. The Double Fold Bias Binder feeds woven binding fabrics only. Use with stretch satin binding to create a professional finish on lingerie and sleepwear maintaining good stretch.