Sorry for my late responce Danny but I’m on a job in the north of Germany with limited time and internet access. The 2 bolts are there to keep the ring with nuts, probably 6 in position. This will allow you to bolt the cover plate on top, with the 6 bolts, without welding on or in the tank. If the 2 bretaining bolts are within the gasket cirkel you only need a gasket between the cover plate and the tank. Hope this explains it. The clean out cover is a similar solution but a bit more sensitive for leaks.