the correct rivet goes either way to hold the rubber seal, the crush end gets to be as flat as the head .... and NO, you can not use pop rivets, they stick out way too much, you need
the correct rivets that can be flattened well on both sides so as not to interfere with either the vent closing [can break the glass] or the smooth sliding of the rollup glass frame .... there are holes where the rivets go, and there are actually 2 sets of rivets, the ones that hold the rubber on the vent post and another 2 or 3 that hold the post/channel to the vent frame
Bill