The capsare placed centrally over min. Ø50 mm cut-outs in the substrate. The base is installed on the bottom layer of the roofing felt in cold bitumen and covered with 2 layers Bitumen, which are stepped on the flange with hot bitumen, cold adhesive or welding. The caps are pressed down over the spout of the base and fastened with a pre-assembled screw. One cap is used per approx. 400 m² of roof, but min. one per closed roof surface.