The headliner board goes covers the entire roof up to about 1/2" to each edge. The rest is covered with all the trim pieces. The main board is held in place by the overhead console, sun visors, rearview mirror and coat hooks in the rear. The two side panels were held on by a hook and clip in between the board and the side part of the roof. That part was a little tricky. Here is a pic of our roof before we put the headliner on...