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Lewis Lifting Device

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A lewis 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, directly 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.

The holes left in the stones are called 'lewis holes'. The holes are positioned in such a way that when the stone is suspended it hangs at the correct angle for bedding. See photographs.

(Wikipedia)