What feature ensures a box trap only allows entry but not exit for the animal?

The feature that ensures a box trap only allows entry but not exit for the animal is the triggered door. This mechanism operates by using a triggering device that, when disturbed by the animal entering the trap, causes the door to close quickly, thus preventing escape.

The effectiveness of this design is crucial in animal trapping. Once the animal is inside, the triggered door secures it by shutting, ensuring the animal cannot easily leave. A simple locked door might allow an animal to exit if it can manipulate the lock or if the door isn’t securely held. A weighted floor may inhibit the trap's movement but does not directly contribute to the functionality of ensuring a secure closure once the animal has entered. A hidden latch could complicate the design but would depend on the animal's behavior to escape rather than a reliable mechanism to trap it securely.

Using a triggered system allows for a swift and reliable capture, which is essential for both effectiveness and humane treatment of the animal by preventing prolonged containment.