[47Merc]

The screws only hold the clamping plate on, not the headliner.
If you remove the clamp plate you will see little teeth on the back of it facing upward. Clean the old liner from these teeth and re-install the plate making sure there is not much gap between the plate and the body.

After you have installed the headliner on the bows and fitted it in the car it will have to be tensioned front to back and then edge of the headliner will be hanging down above the door openings. You then get a dull edged scraper and push the edge of the liner up behind the clamp plate and the little teeth will hold it in place.

The windlace should also be fixed in place before you fit the clamping plates and the Headliner.

You may have to cut some material off the edge of the headliner before you push it in because there is only a limited amount of space behind the clamp plate. Also the reason for the dull edged scraper is because if you use a sharp one you may cut the material as you push it up.