In operative Masonry, the word “Lewis,” is a term for an iron cramp, a device which is inserted into a hole or cavity in a large stone and then attached to a hook and pulley, allowing it to be hoisted to any height and placed into position within the construction of a building or other structure.
The instrument is made of a pair of dovetail wedges, with a hook or ring attached. Inserted into a space specifically crafted in the stone, pulling on the hook or ring spreads and locks the wedges into place. The greater the pull and the heavier the stone, the more securely the Lewis is locked into the hole.
But what meaning does the Lewis have in speculative Masonry?
In English Freemasonry, the Lewis takes on a number of different meanings. It is found among the emblems placed upon the trestleboard of the Entered Apprentice and is used in that degree as a symbol of strength, because, by being employed, the operative Mason is enabled to lift the heaviest of stones with a minimum of effort.
The son of a Mason in England is also called a Lewis as it is his duty to aid the failing strength of his father or “to bear the burden and heat of the day, that his parents may rest in their old age, thus rendering the evening of their lives peaceful and happy.”
According to English Masonic law, a lewis — or son of a Mason — may be initiated at the age of eighteen, rather than the traditional twenty-one.
Thanks to MasonicDictionary.com for the image and background info.