Do you need to have a headboard to put up the material or can you just stick the material up there?

Occasionally we do a headliner in a vehicle that does not have a headliner board. We glue the headliner material straight to the top of the vehicle, (top meaning the metal). It works good enough; however you do have to figure out a way to trim off the edges so that it looks good. With most vehicles that don't have a headliner board, you can tuck the edge under the glass rubber, door rubbers and so on.