Milwaukee Tool’s Smooth Blade Insulation Knife, Serrated Blade Insulation Knife, and Duct Knife stay sharp up to five times longer. The insulation knives feature a full tang and a rounded handle. For added utility, the tools have a lanyard hole for tethering and storage, and also come equipped with a durable blade cover. The duct knife is optimized for cutting duct board, insulation and flex duct. It features a double-edge blade, a full tang and a durable sheath. Milwaukee Tool.