The mark consists of a three dimensional, visible configuration of a folding step. The step is a three dimensional, visible configuration of a clover-leaflet shaped, upwardly facing, stand-on zone bordered by a relatively thin rim defined by a pair of curved side surfaces that angle toward each other as they extend rearwardly from a curved front surface of the rim which joins smoothly with the two side surfaces of the rim, and having a curved elongate front slot with rounded-ends that open upwardly through the stand-on surface. The slot is spaced inwardly from and extending along at a substantially constant distance from the front surface. A crisscrossed pattern of shallow grooves are provided in the support surface of the folding step. The bracket is a three dimensional, visible configuration that includes a middle portion that terminates into a vertical upper end portion. The middle portion includes parallel side surfaces and a front surface that convexly curves upwardly. The upper end portion includes a lower portion with parallel side surfaces and a triangular shaped upper portion in which the side surfaces angle toward each other in the upward direction. A circular opening is formed in the upper end portion. With the exception of solid lines that depict the crisscrossed pattern of shallow grooves that are provided in the support surface of the folding step, the lining that is shown in the mark on the drawing is not a feature of the mark, does not indicate color, and merely represents shading. The broken lines in the drawing are for location purposes only and are not claimed as a feature of the mark.