Usually in modern conversation, the term “kill traps” are often applied to connibears, most commonly used for beaver , and yes, applied correctly, they will instantly dispatch your quarry. The familiar “x” patterned squares, lending themselves to the set type required for most water loving fur bearers. But in the 30’s there was another design that more aptly took the name, “kill traps”. Johny Racquet was a well known trapper who lived and worked the Potsdam area of new york  from the early 1920’s to the late 30’s. His design was a simple one, a round housing with a hole through the center , measuring about 7 and 1 half inch’s in diameter, ,the idea being the critters head would go through the hole. a coil spring inside the housing was wound with a included “trap key”, when a animal’s nose hit the trip wire, the coil spring that was attached to a kill bar, released, in a fraction of a second,quickly dispatching the animal. there were some models with a pan to be stepped on,, rather than a trip wire for a trigger. No suffering was the plus, but, a dead animal in a trap must be removed as soon as possible, or the pelt, and meat, is wasted. i believe that was the down fall of these early “kill traps”. Many collectors seek these out as wall pieces and indeed, pieces of American history. And keep your eyes open when you hunt or scout old properties, you never know what you will find, in the hunting woods.