plastic/rubber



Not a TT, but same deal. Black vent lookin thing (imagine that) on right side of pic

 

yes, plastic frame with rubber flaps. similar function to a dryer vent. one-way airlfow.

once removed exhaust will be drawn in = bad !
once blocked-off/sealed AC or vent air will rush through window seams and make wooshing sound = anoying

best thing to do if yours break is get new ones from audi.
I can give you the part number.
if you are talking about the slots in the trunk lining those are pointless as far as I know, and can be blocked off.

 

tThat's what I meant! Cheers!