Brimmer,

As I recall, you first put the back edge of the cardboard into the metal cross-strip that goes across the middle of the top of the cab. Then you tuck the cardboard under the top edge of the windshield rubber.

The order of installation from rear to front is (I think):
- screw-in rear metal strip
- put rear cardboard in place (I think the cardboard gets tucked behind the door seal/windlace)
- screw-in center strip
- put front cardboard in place (tuck the font edge under the top edge of the windshield rubber)