The Square and Compasses (or, more correctly, a square

Steel square

The steel square is a tool that carpenters use. They use many tools to lay out a "square" or right-angle, many of which are made of steel, but the title steel square refers to a specific long-armed square that has additional uses for measurement, especially of angles, as well as simple...

  and a set of compasses

Compass (drafting)

A compass or pair of compasses is a technical drawing instrument that can be used for inscribing circles or arcs. As dividers, they can also be used as a tool to measure distances, in particular on maps...

  joined together) is the single most identifiable symbol of Freemasonry

Freemasonry

Freemasonry is a fraternal organisation that arose from obscure origins in the late 16th to early 17th century. Freemasonry now exists in various forms all over the world, with a membership estimated at around six million, including approximately 150,000 under the jurisdictions of the Grand Lodge...

. Both the square and compasses are architect

Architect

An architect is a person trained in the planning, design and oversight of the construction of buildings. To practice architecture means to offer or render services in connection with the design and construction of a building, or group of buildings and the space within the site surrounding the...

'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" and learn to "circumscribe and keep us 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

Discernment

Discernment is a term used to describe the activity of determining the value and quality of a certain subject or event. Typically, it is used to describe the activity of going past the mere perception of something, to making detailed judgments about that thing...

.

With a "G"

In English speaking jurisdictions the Square and Compasses are often depicted with the letter "G" in the center. The letter is interpreted to represent different words jurisdiction to jurisdiction. Among the most widely accepted interpretations are that: [G] stands for God

God

God is the English name given to a singular being in theistic and deistic religions who is either the sole deity in monotheism, or a single deity in polytheism....

, and is to remind Masons that God is at the center of Freemasonry. In this context it can also stand for Great Architect of the Universe

Great Architect of the Universe

The Great Architect of the Universe is a conception of God discussed by many Christian theologians and apologists. As a designation it is used within Freemasonry to neutrally represent whatever Supreme Being to which each member individually holds in adherence...

 (a reference to God). In a different context, the letter stands for Geometry

Geometry

Geometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers ....

, described as being the "noblest of sciences", and "the basis upon which the superstructure of Freemasonry is erected."