Masonic Square and Compasses

Square and Compass - about.com
The compass, which is used to draw circles, represents the realm of the spiritual- eternity.
altreligion.about.com/library/glossary/symbols/bldefsmasoniccompass.htm

Square and Compasses
Both the square and compasses are architect's tools, and are used in Masonic ritual as emblems to teach symbolic lessons.
en.wikipedia.org/wiki/Square_and_Compasses
Freemasonry   

Compass and Square - Alchemical Gallery of Medallions
During the granting of the First, Second and Third Degrees, the compass and square are placed upon the altar of the Temple in an interlinked fashion, representing the divine Light as it unites with the candidate and fills him with increasing knowledge.
www.quicksilvermint.com/medallions/pages/compass-and-square.htm