C.C.
Are you talking about a trailer? If so...where in the ceiling would they be? There is really no crawl space up there. Have you seen rats? If not...maybe that's why they haven't taken the bait. There are none. On the roof of a trailer you can hear every little noise....every acorn that falls..every drop of rain. We used to visit my FIL in Carolina...out in the woods...always like listening to the rain. Good Luck