There must be a joint between the fuel tank and the body so that the tank can be installed without vibration and cracks. For the Volkswagen Beetle and Karmann Ghia until 7/1960, the gasket was made of cardboard, which was then replaced by foam rubber. The gasket for the VW Split Bus is made of foam rubber. None of the gaskets have an adhesive layer, which is not necessary for the cardboard version for the VW Beetle and the Karmann Ghia, but it would have been useful for the foam gasket. To install mount the foam gasket on the body by temporarily securing the corners with, for example, a piece of double adhesive tape, after which you mount the fuel tank without the gasket moving.
The fuel tank of the Volkswagen Beetle and Karmann Ghia is secured with special clamps. If you don't have them or if they are rusty, you can get them new. See the "related parts" tab, where the different fuel tanks are also listed.
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