It depends on the setup. Ideally, they're in a building and back-loaded, in which case, they might not even be closed on the backside. Because access to the ba

It depends on the setup. Ideally, they're in a building and back-loaded, in which case, they might not even be closed on the backside. Because access to the back is secured. But for other types of boxes, like outdoor boxes, there's usually another lock along the frame that causes the entire front (or back, depending) to swing open so the mail carrier can efficiently deliver to multiple boxes.