This is the rat bait box I use. There is a partition inside down the middle in the box with a doorway at the far end that the rats and mice have to go around and then along the other side of the partition that is inside in the middle of the box to the bait. There is a little window over the bait so the bait can be checked anytime. Nothing but rat sized or smaller rodents can get to the bait. This is my personal choice from past serious infestations.