I noticed something fierce chewed away at the dog food container in the garage.  So I figured if something would go through that much trouble to get to dog food, why not give that animal dog food along with a cold bar of metal?  So I baited this trap with peanut butter, and put a couple pieces of dog food in it.  Make sure to wedge a piece of paper in the lever so they cannot take the bait back home.  It did not take long for the rats to succumb to the trap. In one week I caught eight, including one on the second floor on the roof.  I just kept re-using the same trap.  You can't find a better price on a dozen rat traps anywhere.