Abstract: A multi-part running board structure mountable on vehicles, including inboard and outboard parts. The inboard part includes a facing plate adapted to abut the side of the vehicle and a step plate which extends substantially normal to the facing plate. The step plate part carries, at its outer edge, a tongue or groove adapted to be interconnected with a tongue or groove carried on a free inner edge of a second part of the running board. The outboard part carries a depending skirt at its outer edge, and a step plate which extends substantially normal to the skirt, and is adapted to be connected to, and positioned in coplanar alignment with, the step plate part of the inboard section. Such connection of the inboard part to the outboard part may be direct or may be through one or more intermediate step plate sections.