Hamsterman, if I bait the trap at night should they be trapped by morning? What prevents them from finding their way out?. This weekend is the big move.
In my experience the answer to this question is yes.
Just be sure to do as another poster said and poke some holes for water flow.
What prevents them from getting out is a basic facet of their behavior.
For whatever reason they often just don't go back out.
Take for example the idea of wasp traps and such that function on a similar principle, small entry into a reservoir, and they seldom find their way back out.