First, remove the brown release paper from the HushMat Ultra Black Foil. Pass the sheet through the largest access hole in the frame and apply it to the inside of the outer doorskin.
Position the sheet against the outer doorskin by using the smaller access holes through the doorframe. Be sure to cover a minimum of 70 percent of the doorskin, starting in the center and working toward the outer edges of the door. This treatment will reduce the vibration of the thin outer-door metal.