Rats around here are not the loathsome Norwegian variety, but rather wood rats, or pack rats, which look like a big mouse, Kinda cute. In the woods, they build pyramids of twigs 3' or so high—rat architecture—always in secluded spots, so you have to be bushwacking to come upon them. In semi-rural areas like this they cruise human habitations for easy pickins. One year I trapped over 40.
For years I used the standard wooden Victor traps and would put peanut better in a little piece of plastic (with punched holes), tied to the trigger with baggie ties. Then I started sheet-metal-screwing a 1/2" copper pipe cap to the trigger, which I filled with p. butter.
I'm writing this after getting one last night that had been eluding me for a week. Outwitted by a rat night after night.
Method: I washed 3 traps (getting rid of scent), smooshed some bacon in the cups, surrounded by smears of Skippy peanut butter—mwah!
And whack! Mighty hunter.