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This type of lewis is the safest to use because it relies on its dovetailed shape for security instead of friction alone, but the seating is time-consuming to prepare.
Their resemblance, once assembled, to a bunch of keys gave rise to an alternative name for them of "St Peter's keys". This has frequently been represented allegorically, drawing the name of "St. Peter" as "the Rock on which I shall found my Church" into an allegory between the fabric of a church building and the community of the church itself. Some illustrations of St Peter even show him carrying a bunch of keys which appear to have no wards. These are not keys in the lock-making sense, but in this sense of stonemasonry.{{
===External lewis===
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In stone yards, a slab lifter is hung from a shed gantry or forklift to transport slabs of stone between storage racks and stone processing machines. It consists of two hinged, weighted friction pads that close astride the top of a slab, and are pulled tightly together by the weight of the slab itself.
The slab lifter uses two safety devices. Safety chains and a support bracket allow safe lifting of large slabs. This lifting appliance also has a safety locking device that is engaged when the gripping pads are activated by the weight of the stone. This prevents any jerking movement from releasing the stone. It is easily disengaged once the slab is secured at its destination.<ref>http://www.freemasonry.bcy.ca/texts/gmd2007/vgmd26.pdf {{Bare URL PDF|date=March 2022}}</ref>
==Gallery==
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