fourfold purchase
- 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.Compare tackle(def 2).
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Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018