I know that this particular pan was leaking around the rivets, so I drilled them out and welded this thing inside and out. It's not pretty, but I know she won't leak from the plates. I could swear I've seen a Bronco dipstick tube with that sort of flange. It serves just like someone said, as a stopper for the hole in the pan and I believe there was some sort of rubber gasket below it to help seal things. Anyone? Maybe I've lost my mind.