Mark the sheet metal where you'd like to cut it with a carbide-tipped scribe, pencil, or marker. Use a piece of wood clamped down as a straight-edge guide for the saw to stay on course.

The blade on a jigsaw is too flimsy to cut sheet metal. Tool School: The Demolition and DIY-Ready Reciprocating Saw Read More Always wear safety goggles and gloves when using a cutoff wheel.