Create locking tabs for resizing rectangular metal duct at the job site. The Malco SL1R Snap Lock Punch raises a louver-shaped projection along the edge of sheet metal that is to be inserted into the rolled lock seam edge of another metal sheet to create a corner connection. The metal pieces snap together and are locked securely. The punch impression is spaced 3/8 in. (9.53 mm) from the metal edge to fit into standard lock seams. A heavy forged cutting jaw and powerful compound handle leverage makes this tool suitable for working in Galvanized steel up to 24 gauge (0.71 mm). Rust resistant nickel plate and black oxide finishes ensure long service life.