Freemason / Masonic lodge flag

The Square and Compasses (or, more correctly, a square and a set of compasses joined together) is the single most identifiable symbol of Freemasonry. Both the square and compasses are architect's tools and are used in Masonic ritual as emblems to teach symbolic lessons. Some Lodges and rituals explain these symbols as lessons in conduct: for example, that Masons should "square their actions by the square of virtue" and learn to "circumscribe their desires and keep their passions within due bounds toward all mankind". However, as Freemasonry is non-dogmatic, there is no general interpretation for these symbols (or any Masonic symbol) that is used by Freemasonry as a whole.

As measuring instruments, the tools represent judgment and discernment.

In English speaking jurisdictions the Square and Compasses are often depicted with the letter "G" in the center. The letter stands for God, and is to remind Masons that God is at the center of Freemasonry. The letter can also stand for Geometry, described as being "the noblest of the sciences", and "the superstructure upon which Freemasonry is founded".