Never had a RAT...but quite a few MICE over the years. I found the only thing that worked were the simple and cheap snap traps....maybe 5 in outside compartments and another 5 inside...various places.
In past years, anywhere between 3 and 5 get it. This year...for some reason NONE. OK..only 1. But the 1.....strange. We had a "warm-up" two weeks ago (50 degrees) for a couple of days, then the cold returned. THAT is when I got the 1 mouse....somehow, he got thru my outer "perimeter", but the interior defense line got him (her).
I found that when I get a mouse, the most "popular" outside area was in/around the generator. Got two traps there.