Abstract: A sheet metal stamping forming an air duct for use in heating and cooling systems and the like. The stamping has a generally rectangular shaped body portion and a protruding tongue portion extending from at least one side thereof. The stamping is foldable along its end edges and the tongue portion whereby two such stampings may be cooperatively engageable with a pair of side panels to form an air duct section having an inlet, outlet and a diverter or secondary outlet formed by the tongue portions. The tongue portions are adapted for connection to standard conventional take-off fittings.