Abstract: An overhead door for the vertical opening of a truck trailer comprises a plurality of panels connected together by hinges, which extend the width of the panels and are confined within the panel. The panels, which are preferably formed of plastic, are counterbalanced by a spring, which is movable with the panels. The spring is wound by gears, which are connected thereto, cooperating with racks on the horizontal portions of the tracks on which the panels are movably supported. The bottom panel is locked to the trailer body by a locking mechanism, which is carried by the lowermost panel and cooperates with locking pins on the mounting angles on which the vertical portions of the tracks are supported.