One of the most common symbols of Freemasonry is the symbol of the crossed compass and set-square. The compass and square are architect’s tools, and symbolize God as the architect of the universe, among other things.
As measuring instruments, the tools represent judgment and discernment.
The compass, which is used to draw circles, represents the realm of the spiritual- eternity. It is symbolic of the defining and limiting principle, and also of infinite boundaries.
The angle measures the square, the symbol of earth and the realm of the material. The square represents fairness, balance, firmness, etc., which is reflected in phrases such as “on the square” and “squared away.” Something that is squared is something that is stable, a foundation for building upon.
Together, the compass and square represent the convergence of matter and spirit, and the convergence of earthly and spiritual responsibilities. The two symbols together form a hexagram, the union of earth with the heavens, matter and mind, etc.
A personification of Geometry with square and compass(Laurent de la Hyre)