Sunshades can either mount onto the window in a surface mount fashion, be direct screwed to the window, use die cast clips to mount, or you could put these sun shades on a window that has lip provisions at the top and bottom whereby you spring load the solar screens that fit into those lip provisions and doing so in that case, the windows are made to accommodate a full sized screen. As shown in this picture, these windows are not made to accommodate full size sunshades, therefore, these sunshades for windows had to be surface mounted.