Abstract: A method of making an aluminum extrusion having a pair of thermal brakes therein and the extrusion, comprising the steps of providing an aluminum extrusion having a pair of side walls, upper and lower wall members, each secured to each of the side walls and a chamber forming a portion of each of the wall members spaced from the side walls, one of the chambers having a continuous bridge member forming a wall thereof and forming the only bridge connecting portions of the upper wall member, the other of the chamber having a discontinuous bridge member forming a portion of a wall thereof, and a "V"-shaped member bridging the discontinuity in the discontinuous bridge member, disposing thermal braking material in the chamber having a continuous bridge member and allowing the thermal braking material to set in the chamber, providing a continuous slit in the continuous bridge member and the V-shaped member to cause a thermal separation of the side walls from each other, placing a leak preventing member in the V-shape