The problem was that didn’t match the whole of screw on metal frame and screws size. Screw couldn’t get through the whole at all. That means I cannot attach those shelves on the wall. I realized it after I put four plastic bases on the wall. I didn’t want to return and exchange during we are all stay at home order in CA. My husband made the metal whole bigger using electric screw driver. I’ve never seen such a miss matching of assemble tool for furniture before.....