B60J—WINDOWS, WINDSCREENS, NON-FIXED ROOFS, DOORS, OR SIMILAR DEVICES FOR VEHICLES; REMOVABLE EXTERNAL PROTECTIVE COVERINGS SPECIALLY ADAPTED FOR VEHICLES
B60J5/00—Doors
B60J5/04—Doors arranged at the vehicle sides
B60J5/0463—Conceptual assembling of door, i.e. how door frame parts should be fitted together to form door
Method of producing polygonal closed cross-section structural component with a curved form and polygonal closed cross-section structural component produced by the method