BMW: What is this??, plastic triangle, seatbelt

Question
What is the function of the plastic triangle that sits on the rear dash between the speakers ?

Answer
Mario,
 I'm assuming you are talking about the seat belt holder.  The center seatbelt in the rear plugs into this to keep it neat looking in the back.  Take the male end of the seatbelt, and plug it in to this triangle and then pull the belt tight.
 Hope this helps,
 Josh