Abstract: The invention relates to an assembly device (1) and to a method to reliably mount containers (3) fitted with a self-supporting structure (4), in particular plastic containers (3) for liquid media and chemicals such as liquid engine-fuels, for affixation on stationary or displaceable supports (2). The method comprises the steps: affixing conduits to a support (2); affixing the container (3) on the support (2); and connecting the container (3) to the conduits; where the step of assembling the container (3) to the support (2) includes affixing one connector part (8) each on the support (2) and on the container (3) as well as joining to each other the connector parts (8). Preferably the connector part (8) shall be affixed on the support (2) before the step of affixing the conduits. The assembly device (1) comprises means with which to carry out said method.