Looking at Gregg's profile #10 I would hazard that they are extensions for the wheel scotch holders that uses them as a step. The reference is vague but makes sense that some sort of extension could be stored there that adds an additional rung to the holders on each side just underneath. in the pictures you see the scotch holders, not the scotches and as there is no tailgate there is no other step unless you add one low enough. without one they appear to be to high to put your foot in to get up in the back. My thought
