Some people mistakenly believe that a coffin is a tapered hexagonal or octagonal box used for a burial, and that a rectangular coffin ought to be called a "casket" instead. This is a euphemism invented by the funeral director's industry. They are all coffins, regardless of shape, and regardless of the amount of upholstery they contain.
Coffins have been traditionally made of wood. Until the late nineteenth century, it was common for coffins to be made to order by carpenters in the United States of America. Eventually, the manufacture of coffins became a national industry, and dealers were typically in the furniture business. The traditional, hexagonal pine coffin gave way at this time to the rectangular model. Metal, fiberglass, particle board (chipboard) and cardboard coffins are available today. While the less durable materials are usually chosen on grounds of cost, they may also be chosen out of environmental concern; cardboard coffins are generally used in woodland burials.
A coffin may be buried in the ground directly, or placed in a concrete vault. Some countries practice one form almost exclusively; in others it merely depends on the individual cemetery.
Coffins have not always been used in the Western world. They were formerly the prerogative of the wealthy and noble. The poor were buried in a shroud in the churchyard; the wealthy, in a coffin in the crypt of the church building itself.
Other cultures that practice burial have widely different styles of coffin. In some varieties of orthodox Judaism, the coffin must be plain, made of wood, and contain no metal parts nor adornments. These coffins use wooden pegs instead of nails. In Africa, elaborate coffins are built in the shapes of various mundane objects, like automobiles or aeroplanes.