fourfold purchase
noun
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).
Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019