ANIMAL TRAP
A toothed guillotine door whose springs are hidden from the mouse.
The animal enters through an opening in the housing and steps onto a hinged trip pan bearing baited spike. The pan's depression swings an L-shaped lever forward, and a roller on the lever lifts a finger on the trigger crank, freeing it from a catch on the raised door. Retractile coil springs, concealed along the sides of the opening, pull the sliding door down through its guideways. The serrated lower margin of the door meets a matching toothed strip below the entrance, impaling the animal.
“This causes the roller 42 to raise the finger 35 and swing the trigger 31 free of the catch 34 so that the springs 26 forcibly close the trap door 21 and impale and almost, if not actually, kill the animal at once.”— Charles A. Kalina, from the specification
And the world did not beat a path to his door.