The Square and Compasses (or a square and compasses connected together) is the most well-known symbol of Freemasonry. The square and compasses are tools used by architects. In Freemasonry, they are symbols that teach important lessons.

Some groups within Freemasonry explain these symbols as lessons about how to act. For example, a book called Duncan's Masonic Monitor from 1866 says: "The square teaches us to act fairly. The compasses teach us to stay within limits and treat others kindly." However, Freemasonry does not have official teachings, so there is no single meaning for these symbols (or any Masonic symbol) that all Freemasons agree on.

The name "Square and Compass" was used by two national college groups started by Master Masons. These groups were called Square and Compass and a later group named Sigma Mu Sigma.

With a "G"

In many English-speaking countries, the Square and Compasses are shown with the letter "G" in the middle. The letter "G" has several meanings, depending on how it is used. Most often, it stands for God. It can also represent Geometry, reminding members of Freemasonry that Geometry and Freemasonry share the same meaning and are described as "the most important science" and "the base upon which all of Freemasonry and everything in the universe is built." In this context, the "G" may also stand for Great Architect of the Universe, which is a way to refer to God without mentioning a specific religion.

Use of the symbol by other fraternal bodies

The square and compasses have been used as a symbol by several organizations, and are sometimes accompanied by other symbols: