There are three inlet positions in the top of the tank, select the position that suits your site.

Using an electric jigsaw or holesaw, cut around the indicator ring of the inlet position you wish to use.  To start the cut, drill a hole just inside the ring to enable you to insert the blade of your jigsaw. It is not critical that you get the hole exactly right as the inlet strainer will overlap the hole by a small amount, but do try to stay close to the indicator ring.

Secure the inlet strainer using the screws provided.  If you need to clean the strainer or access the tank, remove the screws and then the strainer.

Never climb inside the Fatboy tank.