A bed of nails is typically an oblong piece of wood, the size of a bed, with nails pointing upwards out of it. It appears to the spectator that anyone lying on this "bed" would be injured by the nails, but this is not so, assuming the nails are numerous enough, since the weight is distributed between them such that the force exerted on each nail is not enough to break the person's skin. In geometry, a rectangle is a defined as a quadrilateral polygon in which all four angles are right angles. ... A pile of nails. ...

One use of such a device is for magic tricks or physics demonstrations. A famous example requires a volunteer to lie on a bed of several thousand nails, with a board on top of him. Cinder blocks are placed on the board, and then smashed with a sledgehammer. Despite the seemingly unavoidable force, the volunteer is not harmed: the force from the blow is spread among the thousands of nails, and the breaking of the blocks also dissipates much of the energy from the hammer. Magic, including the arts of prestidigitation and conjuring, is the art of entertaining an audience by performing illusions that baffle and amaze, often by giving the impression that something impossible has been achieved, almost as if the performer had magic or supernatural powers. ... Physics (Greek: (phúsis), nature and (phusiké), knowledge of nature) is the science concerned with the discovery and understanding of the fundamental laws which govern matter, energy, space, and time and explaining them using mathematics. ... A stack of rectangular cinder blocks A cinder block (also mistakenly called a concrete block), breeze block, or Concrete Masonry Unit (CMU), is a rectangular block or brick used in construction. ... A sledgehammer. ...

This demonstration of the principles of weight distribution requires that the weight of the volunteer be spread over as many nails as possible. The most dangerous part is the moment of lying down or getting up, when one's weight may briefly be supported on only a few nails. Some "beds" have rails mounted at the sides to help users lie down and get up safely.

The bed of nails is also used by some for meditation. A large statue in Bangalore depicting Shiva meditating Meditation describes a state of concentrated attention on some object of thought or awareness. ...

Use in electronics

In electronics, "bed of nails" can also refer to a type of device used to connect a printed circuit board device under test (DUT) to automatic test equipment. Named by analogy with a real-world bed of nails, these devices contain an array of small, spring-loaded pogo pins; each pogo pin makes contact with one node in the circuitry of the DUT. By pressing the DUT down against the bed of nails, reliable contact can be quickly, simultaneously made with hundreds or even thousands of inidividual test points within the circuitry of the DUT. The hold-down force may be provided mechanically or by means of a vacuum pulling the DUT downwards onto the nails. Close-up photo of one side of a motherboard PCB, showing conductive traces, vias and solder points for through-hole components on the opposite side. ... Device under test (DUT) is a term commonly used to refer to a manufactured product undergoing testing. ... Automatic test equipment is any automated device that is used to test printed circuit boards, integrated circuits, or any other related electronic components or modules. ... A pogo pin is a device used in electronics to establish a (usually temporary) connection between two printed circuit boards. ... Look up Vacuum in Wiktionary, the free dictionary. ...

Devices that have been tested on a bed of nails tester may show evidence of this after the fact: small dimples (from the sharp tips of the pogo pins) can often be seen on many of the soldered connections of the PC board.

External links

• Australian Skeptics -- how the bed of nails works and how to make one
• DarylScience's E-World -- the bed of nails in use as a school physics demonstration