These little cubes are designed to prevent your art glass from stressing the wall fixings. They are only required if you want (or need) to bond the hanger towards the top of a panel or if the panel is tall. They keep the piece parallel to the wall and for panels up to 20cm wide, place one centrally about 25mm from the bottom edge. On wider panels, one on each bottom corner is best. They are self-adhesive so you can just pop them on before hanging the panel.