He told me that the idea behind the 4 doors. When the trap is say 6x12 a single door will be 11x 7or 8 inches. That is a pretty good sized door for a rat to push. But when you put the center divider in you can use 2 doors 5x7 or 8 inches long actually less then half of the single door. That is why he made it with the 4 doors.