WARNING: This page is about a different car, the 2004 Volkswagen R32. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Driving In Sealing Plugs Using Drift 3264
Courtesy of VOLKSWAGEN UNITED STATES, INC.
Drive in sealing plugs using drift 3264 to dimension - a
-. This is approx. 3 mm under lower edge of housing.