If you need to cut a hole in the middle of a sheet of metal duct, Malco’s CDR duct ripper will get you started. Designed especially for puncturing and ripping ductwork, this tool looks somewhat like a standard blade screwdriver, but the similarities end there.
Malco grinds the tip of this hardened, corrosion-resistant blade to a perfect angle for puncturing sheet metal. A hanging hole penetrates the cushioned grip for easy storage. If you don’t want to ruin a perfectly good screwdriver, you can pick it up for about $12.