The Deeper Symbolism of Freemasonry from The Meaning of Masonry by Walter Leslie Wilmshurst.

“It has always been the custom for Trade Guilds, and even for modern Friendly Societies, to spiritualize their trades, and to make the tools of their trade point some simple moral. No trade, perhaps, lends itself more readily to such treatment than the builder’s trade; but wherever a great industry has flourished, there you will find traces of that industry becoming allegorized, and of the allegory being employed for the simple moral instruction of those who were operative members of the industry.” [via]