Some form of the "Square and Compasses" is the most
widely used and known symbol of Masonry. In one way, this symbol is a kind
of trademark for the fraternity, as the "golden arches" are for
McDonald's. When you see the Square and Compasses on a building, you know
that Masons meet there.
And like all symbols, it has a meaning.
The Square symbolizes things of the earth, and it also
symbolizes honor, integrity, truthfulness, and the other ways we should relate
to this world and the people in it. The Compasses symbolize things of the
spirit, and the importance of a well-developed spiritual life, and also the
importance of self-control -- of keeping ourselves within bounds. The
"G" Stands for Geometry, the science which the ancients believed most
revealed the glory of God and His works in the heavens, and it also stands for
God, Who must be at the center of all our thoughts and of all our efforts.
Source: The Masonic Information Center, 8120, Fenton Street, Silver Spring, Md., a division of The Masonic Service Association.