Can be done many ways. Later model vehicles use RTV. Older ones gaskets. Even though the surfaces are the same for the old stuff and the new stuff. I like a gasket and I glue it to the cover with gasket adhesive to keep it in place. And it's easier to clean off the cover next time than the housing (laying underneath the car). The last time I used RTV, I had to take it off and redo with a gasket. And I had cleaned it off with brake cleaner before I put the RTV on. With RTV though, somebody on here, ?was it 5-90 (maybe for valve covers)?, suggested just snugging it down, waiting for it to harden up good, then tightening again. But I like gaskets.