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Meaning of fourfold purchase

four'fold pur'chase

Pronunciation: [key]
  1. a tackle that is composed of a rope passed through two fourfold blocks in such a way as to provide mechanical power in the ratio of 1 to 5 or 1 to 4, depending on whether hauling is done on the running or the standing block and without considering friction. Cf. tackle (def. 2).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.