If a creature goes inside, the box should slam shut.
Setting the trap
A box trap is an item used in the Hunter skill. Once the trap is set, a small creature entering the box should be trapped inside and can be captured alive. It is possible that the trap will fail to catch its prey, and a trap will collapse by itself after some time. A minimum of 27 Hunter is required to use box traps, at which point the player can capture ferrets.