Abstract: The thermal induction unit utilizes heat rays radiated by external material bodies by virtue of their absolute temperature and by reflection. The majority of the surface area of the thermal induction unit is fabricated of heat insulation material so as to inhibit heat transfer therethrough and passages are provided throughout the otherwise insulated area. The structure on the induction side of the unit is so conformed as to reflect, direct and converge radiant heat rays through the passages and thus into the environment on the opposite side of the induction unit.

Abstract: A fastener is disclosed for fastening together two sheets of metal having mutually aligned apertures defined by generally annular walls having a plurality of radially spaced notches therein. The fastener comprises a metallic tube having a plurality of outwardly projecting tabs positioned along chord extensions of the tube and sized to be seated in the aperture defining wall notches of the two sheets and bent off the chord extensions of the tube into locking engagement with the aperture defining wall notches to fasten the two sheets of metal to the fastener and thereby to each other.A method is also disclosed for fastening together two sheets of metal. The method comprises the steps of cutting similarly sized and configured apertures into the two sheets of metal with the aperture defining wall of each sheet formed with a plurality of radially spaced notches. The two sheets of metal are stacked together with the aperture defining walls of each sheet in mutual register.