Gripnail is a proven mechanical fastener used to attach insulation to the inside of sheet metal duct work. The hardened tapered teeth pierce the duct liner and form a positive attachment to the sheet metal. Each fastener is precisely formed to exacting quality control standards adn they may be applied with a variety of tools or equipment. Gripnails only work when the sheet metal is supported by a hardened steel plate or the anvil of a Gripnailer.