ANIMAL TRAP
The trap engages its own safety catch, in case the user forgets.
Spring-loaded serrated jaws are held open by a toggle mechanism at dead center. The mouse swings a pendulum trigger, which shifts the toggle out of dead center; the springs snap the jaws shut. As the jaws close, a rigid finger on one jaw strikes a pivoted spring-steel strip, forcing a lug on the strip into an opening in the opposite jaw. The safety catch is thereby re-engaged automatically before the user handles the trap again.
“The primary object of the invention is to provide a safety catch device to be affixed to the trap described in the above-stated patent, and it is intended to provide such a safety catch device as will embody means protecting the user from the possibility of injury while handling the trap, and to provide in addition automatic means for engaging the safety catch, thereby avoiding the possibility of the user's forgetting to set the catch while handling the trap.”— Mary A. Clayton, from the specification
And the world did not beat a path to her door.