an improved side step for motor vehicles designed to mount to tubular side bars . the step includes a mounting insert for placement within the tubular side bars and having structure for attaching the step thereto . the mounting insert fits within an elongated aperture in the tubular side bar , the aperture having a width smaller than the width of the insert . the insert includes a plurality of apertures within which locking members extending downward from the step are secured . the step also includes a pair of end tabs for securing the longitudinal ends of the step under the edge of the aperture in the tubular side bar . the step is provided with a preferred grid of ribs and channels to reduce the amount of material required while providing adequate strength for the step . in one embodiment , the step curves partly around a bend in the tubular side bar .