How to Measure and Cut a Steel Panel for a Vent

Stretch a tape measure across the horizontal edges of venting that you need to fill with a new steel panel. Write down the measurement. You will cut the panel so that it is flush with the existing sides, so do not add or subtract anything from this measurement. Repeat the measurement on the vertical edges of the vent.

Lay a piece of sheet metal on a solid, flat surface such as the driveway or garage floor.

Lay out the tape measure on top of the sheet metal and make two marks about 12 inches apart at the points that correspond to your measurements of the opening on the vent. Lay a straightedge, such as a yardstick, along each set of marks so that the stick aligns with them, and draw straight lines using a marker.

Cut along the lines using tin snips or electric shears. Take your time and cut as straight as possible.

Place the cut sheet of steel against the opening on the vent. You may need a helper to hold it in place as you inspect the sides to make sure they align with all four edges of the vent. If there is any overlap, shear it off with the tin snips until the sheet is as straight as possible.

Seal the steel sheet in place against the vent by applying a layer of foil-covered vent tape around all four edges. The tape will seal the gaps between the pieces, preventing air leakage, and make for a finished appearance.