Steel frame construction consists of 13-gauge inverted “U” shaped cross members mounted on 11-gauge inverted hat channels. The crossmembers span the chassis frame at approximately 26" intervals and extend the full width of the body. The frame is finished with a 2" x 2" x 11-gauge steel angle around the perimeter. Each vehicle has OEM standard cross-members. F-550 models have 4-gauge steel frame extensions that are welded at the rear of the OEM frame rails.
The sidewall construction consists of 1" x 2" x 16-gauge vertical steel tubes formed for body contour. These tubes are welded at the top of the wall to a 1" x 2" x 16-gauge steel header tube and at the bottom to a 1" x 1" x 16-gauge footer tube. Both the header and footer tubes run the full length of the unit body on both sides.
The entire sidewall assembly is welded to the 2" x 2" x 11-gauge perimeter floor angle.
Attached to the top sidewall rail construction are formed roof bows. These are made of 1" x 1" x 16-gauge steel, formed to match the roof contour. The roof bows are welded to the 1" x 2" x 16-gauge top side-wall tubes from front to rear of the body assembly. There are double bows throughout the cage assembly added in for additional strength. Additional steel plate is welded in strategic locations to provide additional strength where needed.
The front of the ceiling includes an additional vehicle support called the “super bow”. This assembly is two formed roof bows encased by a formed 10-gauge plate, welded in the same manner as the rest of the vehicle bows. The combination of these systems allows for superior roof structure strength.