Lewis (lifting appliance)
Device used to grip stones for lifting / From Wikipedia, the free encyclopedia
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For other uses, see Lewis (disambiguation).
A lewis (sometimes called a lewisson) is one of a category of lifting devices used by stonemasons to lift large stones into place with a crane, chain block, or winch. It is inserted into a specially prepared hole, or seating, in the top of a stone, preferably above its centre of mass. It works by applying principles of the lever and utilises the weight of the stone to act on the long lever-arms, which in turn results in a very high reaction force and friction where the short lever-arms make contact with the stone inside the hole and thereby prevents slipping.