The lewis is a tool used in operative masonry to lift large stones into place. They are tripods that sit securely in place and support the freshly cut stone. Its historical use has been proven to exist as far back as the early Romans. It is still used today in many different professions including car mechanics to help lift heavy engines into and out of vehicles.
In speculative Freemasonry a Lewis is the son of a Freemason who is joining the fraternity. This analogy it is commonly used to show that the father raised the son into position to take his place as part of the structure of Freemasonry.