An improved vehicle box assembly with an upright front or side panel defined by a monolithic one-piece roll-formed steel sheet member having a desired three-dimensional configuration. The sheet steel member is roll-formed in the lengthwise direction thereof. The panel has a channel, preferably a closed tubular channel on the front panel, roll-formed along one edge of the sheet steel during forming of the panel. The closed tubular edge rail is preferably closed by a seam weld which extends lengthwise therealong and is performed in line with the roll-forming operation. The roll-formed panel is preferably provided with a flat shelf deformed horizontally to extend lengthwise along the panel downwardly from the top rail.