Klein Tools Serrated Duct Knife is perfect for cutting duct board and flexible duct. The stainless steel blade is dual-sided: 1-serrated and 1-regular for added versatility. Knife comes with a puncture resistant nylon sheath. Klein Tools Serrated Duct Knife is perfect for cutting duct board and flexible duct. The stainless steel blade is dual-sided: 1-serrated and 1-regular for added versatility. Knife comes with a puncture resistant nylon sheath. Cuts duct board and flexible duct Double-edged knife blade, fine edge on one side and serrated edge on the other Puncture resistant nylon sheath with belt loop Cushion-Grip™ handle for comfort Klein Tools Serrated Duct Knife is perfect for cutting duct board and flexible duct. The stainless steel blade is dual-sided: 1-serrated and 1-regular for added versatility. Knife comes with a puncture resistant nylon sheath.