I bought this thing a couple of years ago to install an oil pressure gauge, but I'll be damned if I can remember how to put it on... I know it goes between the block & filter, but does it just get held in place when I screw the filter down?

Or does one of the brass extensions screw onto the threads that the filter attached to first, which holds the sandwich adapter on??

Confused...

 

you use the brass adaptors to hold the sandwich on.