The Fortress Box Frame Roller Gate, manufactured by Tymetal Corp., represents a dramatic breakthrough in the design, construction and performance of large roller gates by using a specially designed wheel system. Double clear openings up to 500 feet have been protected using this design. When the gate is operating under normal load, the wheels run on the flat surfaces of the top and side of a steel beam. As wind begins to put lateral pressure on the gate, the width of the wheel system and its low center of gravity tends to keep the gate in place. However, when the wind load is strong enough to cause the wheels to lift from the beam, the safety guides come in contact with the underside of the top flange of the track and the gate remains safely anchored to the ground.