ANIMAL-TRAP
A trap whose grip improves as the caught limb swells.
The base is bent from a single piece of metal, its upturned ends serving as pivot posts for two spring-actuated jaws. A dog and bait pan hold one jaw open; the animal disturbs the pan, the dog releases, and the jaws close on the leg. The jaw faces carry shallow indentations or diagonal cross grooves rather than teeth. The gripped member swells, pressing flesh into the recesses and tightening the hold without cutting.
“The member gripped between the jaws becomes inflamed and swells, thus causing the flesh of the animal to be pressed into these indentations or grooves and makes it practically impossible for the animal to withdraw the entrapped member, either lengthwise or transversely of the jaws.”— Reuben C. Eldridge, Julius Willers, from the specification
And the world did not beat a path to their door.