There's not a lot of peanut butter on the board--but there's quite a lot of feed in the four-foot high plastic or cardboard barrel. Besides, rats are naturally curious, and mice are naturally stupid. Just leave enough empty space that the larger rats can't jump out. Feed's kind of like sand, which helps--it's difficult to launch off a sliding surface.OMG - that's brilliant! How tall is a plastic feed barrel? I understand why the rodent would follow the p.butter trail up the board, but how do you get them to jump into the barrel? Really love this idea - please tell me more!