Carried by Gunold for decades since it's so effective, this classic film permanently seals patches and emblems onto all commonly used fabrics. Supplied as a film on silicone release paper. You won't be disappointed! Gunold Heat- N' Seal™, or BSN™ film, is a special film that allows an embroiderer to obtain a permanent bond of appliqués, embroideries, patches, and emblems onto almost any fabric. Applied by a household iron or heat press, it supplies a permanent bond, including edges, borders and seams. For decades it’s been one of our most popular items. BSN™ is available in two different versions: one washable up to 104° F (for delicates) and one washable up to 203° F (for industrial applications).