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Speaker 1: Welcome to brain Stuff from how stuff works dot com,

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Speaker 1: where smart happens the high on Marshall Brain with today's question,

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Speaker 1: can you explain the diameter measurements used in nails? You

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Speaker 1: can buy nails ranging from twopenny up to sixtypenny in

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Speaker 1: the United States, represented as two D or sixty D, respectively.

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Speaker 1: When you buy a twopenny nail, what you're buying is

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Speaker 1: a nail that is an inch long. A threepenny nail

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Speaker 1: is an inch, and a quarter fourpenny is an inch

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Speaker 1: and a half, and so on, increasing by quarter inches.

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Speaker 1: That works up to a twelvepenny nail. So a twelvepenny

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Speaker 1: nail is three and a quarter inches long, a sixteenpenny

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Speaker 1: nail is three and a half inches long, a twenty

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Speaker 1: penny is four inches, and after that there's the thirty, forty, fifty,

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Speaker 1: and sixtypenny nails, each one a half inch longer than

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Speaker 1: the last, So a sixty penny nail is six inches long.

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Speaker 1: Why is D used instead of P when talking about

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Speaker 1: pennies and nails? For example, a two D nail is

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Speaker 1: a twopenny nail. It probably comes from the Roman coin

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Speaker 1: called the denarius. It's not clear that anyone knows where

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Speaker 1: the penny designation comes from, though it might have indicated

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Speaker 1: the cost of a hundred nails of a given size

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Speaker 1: in the four hundreds, but who knows. For more on

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Speaker 1: this and thousands of other topics, is it how stuff

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Speaker 1: works dot com