Scientists describe the mousetrap as a device that is "irreducibly complex." The mousetrap cannot be made more simply and still function, and, at the same time, it is so simple and does its job so well that it gives the illusion of being a profound achievement. "To build a better mousetrap" means to achieve an ideal, to reach a pinnacle of achievement, or to create the best possible device in an imperfect world.


Traps as simple as pits dug in the ground have been used since humans began to hunt for food or to kill predators and vermin. The needs to catch prey and to protect the earliest settlements first motivated our ancestors to devise means of catching small and large animals for food and clothing. As early man learned to grow a wider variety of food and domesticate animals, trapping changed. Animals that raided farmyards, fields, and grain supplies had to be stopped, and the trapping of wild animals as a part of hunting became a sport, rather than a necessity.

More recently, animals have been trapped in the wild for medical research, although the most commonly used research animals—the laboratory mouse and rat—have been bred for this use. And city dwelling, heated houses, and stored food supplies have invited the "country cousins" of these laboratory animals to share our homes. When they feed, live, and breed where they are not wanted, traps, poisons, and the family cat have been used to keep their numbers down or eliminate them entirely.

The traditional snap mousetrap is a primitive device made of a combination of simple machines. It works—sometimes. However, it has enough flaws in design, operation, the process of baiting the trap, the resulting killing, and the calculated ability of the mouse to outsmart it that the objective of "building a better mousetrap" has become the inventor's watchword. Our culture has also evolved in its level of humanitarian concern and the desire to live trap even the most pesky animals so they can be released in the wild. The second major class of mousetraps that has been invented is the cage trap.


In 1895, John Mast of Lancaster, Pennsylvania, invented the snap-trap. Many other inventors had produced devices for killing mice before that date, but Mast's design was brilliant in its simplicity—and it had the advantage of not catching in ladies' long skirts of the day. Mast's simple trap enticed the mouse with a bit of bait held in a bait pedal and dispatched it with a striker that struck within three milliseconds of the mouse's fatal nibble.

Mast made a small fortune from his invention and sold his company in 1907 to Oneida Community Ltd. Known for its production of silverware, Oneida was also a manufacturer of steel traps that used its profits to supplement local fanners in what is now called Oneida, New York. Woodstream Corp. in Lititz, Pennsylvania, purchased the mousetrap business from Oneida, and, today, Woodstream manufactures up to 10 million mousetraps per year that are close cousins to Mast's original invention. Part of the beauty of the snap trap is its low price. In 1900, it retailed for five cents and, in 1962, it was still available for seven cents.

Many have followed in Mast's footsteps and have attempted to improve on his idea. Since 1838 when the U.S. Patent Office was opened, 4,400 patents have been granted for mousetraps, although less than 25 such inventions have made their creators any profits. The Patent Office has 39 official subclasses for mousetraps that read like an index of the Chamber of Horrors and include choking, squeezing, impaling, non-return entrance, swinging killer bar, explosive, and constricting noose devices. Electric mousetraps that dispatch victims with a shock, and various shapes and sizes of plastic and metal traps that conceal the mouse remains have been created but have not achieved commercial success.

In 1924, a janitor in an Iowa school witnessed an infestation of mice in the school. He turned his attentions in the evenings to building a better mousetrap in his garage. The resulting invention, called the "Catch-All Multiple Catch Mousetrap" would trap a mouse without killing it, allow its release, and could be reset for the next capture. A. E. "Brick" Kness went on to found Kness Manufacturing in Albia, Iowa. Today, Kness Manufacturing builds a standard snap-trap that has a plastic base instead of a wood one and the metal and plastic "Catch-All." The company is one of approximately three in the world in this industry and markets to 14 countries.

Raw Materials

The raw materials for the snap trap include pine for the base, a metal killer bar or striker that is driven by a 15-gauge coil spring, a thin metal rod called a trigger rod, and a bait pedal that is another small square of metal. Staples hold all the pieces together.

For the cage trap, sheet steel is used to form the basic box, and plastic is used to form the internal workings. Both materials are supplied by outside producers and formed in the mousetrap factory.


The design of the cage trap is also relatively simple. The cage typically has six sides, and one of these is the rodent's entrance—but not an exit. Some cages have two inescapable entrances. Most are equipped with handles and with sliding release doors so the captured rodent can be released in the wild. The design lies in understanding the habits of the animal being trapped. A large but slow animal requires a cage made out of stronger materials, but the door mechanism can close securely but simply. For the wily house mouse, an inexpensive, portable, lightweight trap with swift-action doors is needed to capture it before it escapes. Ease of baiting the trap, its reusability (called repeatability), the number of animals it can capture and hold, types of construction materials, and other factors are design considerations.

The cage also contains a trip pan where the bait is placed. The trigger rod is attached to the trip pan so, when the bait is taken, the exit slams shut. The tension required to activate the trip pan and its trigger rod are set in the factory and are designed for the weight of the animal. Cage traps for mice are made of steel to limit opportunities for the animals to try to chew through wire.

The Snap Trap

The base of the snap trap is made of wood or plastic, depending on the manufacturer. Pine is used because it is solid and relatively inexpensive. Plastic can also be injection-molded with sites to hold the metal parts on the base, termed the mouseboard. The bait pedal is a small piece of die-cut metal with bait mount and a nub on it that allows it to pivot very slightly within the confines of its staples. The pivoting action releases the trigger rod and striker no matter how slightly the mouse moves the bait.

Some manufacturers use hand labor to assemble snap traps, however at least one maker has a fully automated process. In the automated process, copper-coated strands of steel are extruded and shaped into the trigger rod and striker. All metal parts are attached to the mouseboard with metal staples that extend through the mouseboard and crimped into the board so the pieces do not easily pull apart.

The Manufacturing

The manufacturing process of the catch-all metal trap is described below.

A traditional mousetrap and two types of cage traps.
A traditional mousetrap and two types of cage traps.

  1. Sheets of galvanized steel are delivered to the factory for die cutting. The steel is termed "G90 Lock-Forming Quality" steel that is chosen for its strength characteristics and durability. The sheets of steel are precut into six different widths. Outside suppliers also deliver pellets of high-impact polystyrene for use in making the internal parts of the cage.
  2. The body, ends, lid, and paddle are all made of galvanized steel. The various widths of steel are run through dies specific to each width and trap part. These dies further cut, punch, notch, and form the pieces of the cage. The dies exert pressures ranging from 5-40 tons (4.5-36 metric tons), depending on their purposes. All of the metal piece parts go through the die machine.
  3. Meanwhile, the plastic pellets are melted in an injection molding machine that forms the pieces of the trip assembly. All of the metal and plastic pieces are transported by conveyor belt to the assembly line.
  4. The parts of the cage trap are assembled by hand. Operators at eight different stations snap the pieces of the body together first. The trip assembly is also snapped together and inserted in the body. The trip assembly operates because of a wind-up mechanism that also allows it to be rewound (that is, the tension is reset) and reused. At the last sequence of assembly, the trip is wound up and tested. One hundred percent of the cage traps are tested before they are placed back on the conveyor and transported to packing and shipping. The cage traps are wrapped singly and then packed in quantities for shipment and sale.

Quality Control

Quality control for the cage traps is intensive. Because the traps can be used many times, they must be constructed to last for a long time and to maintain their appearance. Each piece part is checked by hand before assembly, examined for cosmetics, and measured for exact dimensions. The line operators are responsible for rejecting pieces or partially assembled cages if they do not snap together properly.


There are no byproducts from manufacture of either type of trap, but most makers produce other varieties of traps for larger animals. Wood waste is disposed. Both metal and plastic waste are segregated and returned to their suppliers where they are remelted and recycled.

The Future

The future of the two most successful forms of the mousetrap—the snap trap and the cage trap—will be secure as long as mice are with us. Both the snap and cage traps have seen minor evolutionary changes, but, essentially, they are near-perfect inventions. Agriculture is becoming more limited in area but generating higher density production, so protection of harvested and stored crops from vermin is essential. In urban settings, more crowded living conditions result in increases in rodent populations, making traps a necessity. People are also more interested in saving the lives of the creatures they capture, so humane traps are increasingly popular in the United States and other countries, thus broadening the marketplace for American manufacturers. Competition in building the better mousetrap is limited except, perhaps, for that best mousetrap of all—the cat.

Where to Learn More


Meyer, Steve. Being Kind to Animal Pests: A no-nonsense guide to humane animal control with cage traps, 1991.


Fenn, Donna. "A better mousetrap." Inc. (March 1985): 69.

Hope, Jack. "A better mousetrap." American Heritage (October 1996): 90.


Kness Manufacturing Co., Inc. .

"A Mousetrap Is Irreducibly Complex." .

Seabright Laboratories. .

McGuire, Odell. "The Slidewhistle Mouse-trap." December 21, 1995. .

Gillian S. Holmes

Also read article about Mousetrap from Wikipedia

User Contributions:

Sorry, but this statement is totally non-factual: "
Scientists describe the mousetrap as a device that is "irreducibly complex."

Only creationists (a.k.a., intelligent design advocates) present this argument as irreducibly complex. It is their byword, but unfortunately the argument it totally specious. There are many, many types of mouse traps, so to say any particular one is irreducibly complex is utter nonsense. But it is the basis for the creationist's argument that things are far too complex to have originated by random chance, thus they argue that some unknown force (God to them, though they refrain from publically stating so though they tell the church groups they preach to that that is the case) is behind the mouse trap, and us. It's a simplistic, non-scientific argument that is used by creationists, but again it is a worthless argument. I am surprised you've used the term in this article without understanding its origin, unless, of course, you support creationism/intelligent design, which is a highly anti-scientific, religion based attempt to discredit science.

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