That's the boot that the door check rod retracts into when the door is
closed. It fits over the check rod's attachment point/bracket inside
the front, bottom edge of the front doors. It's there to keep out dust
& moisture.
-Simon

On Wednesday, October 16, 2002, at 09:07  PM, George Goff wrote:

> Yesterday, I found a small, blow-molded, black plastic part loose and
> lurking
> under my rear seat.  It is marked with the letters "RHO", the VW/Audi
> logo
> and part no. 251 837 267.  It looks like a container about 1 1/2" X 2"
> X 4"
> with the open end reduced to about 1" x 1 1/2".  Does anyone know what
> this
> is and, more importantly, where it belongs?  As clean as it is, both
> inside
> and out, it looks almost like it could be some kind of acoustical
> tuning stub.
>
> George
>