Attachment points for tonneau cover

[acmack]

How is the rear end of the tonneau cover secured to the deck?
My rear deck has a row of standard snaps to secure my rear sear cushions but also has a row of 11 speed snaps 1 inch below the seat snaps. Are these speed snaps a factory item and intended to secure the tonneau cover? I have seen very few GPA's with these snaps.
My deck is the earlier model that does not have the additional middle stiffening rib stamped in it.
Maybe the snaps were only installed early on, then deleted?