What are the (4) openings /covers on the roof. What are they called..???

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On the 2011 Panamera Turbo (Actually any Model) ...there are (4) openings which are covered over each door the roof.These covers are (approx) 1/2 in x 3ins ....What is the function of these openings in respect to the roof. (One of the covers (over the passenger side) has come apart and needs to be re-attached. (My 99 Carrera have the same covers/openings ....but they are in tact..!..) What is the part called....???