Construction tools didn’t evolve much between Antiquity and the Middle Ages, they even stayed pretty much the same until the 19th century. The above tombstone of Hugues Ligergier, the ”maître d’oeuvre” (master builder) of Reims cathedral, shows the three most important tools of the medieval architects: ruler, square and compass.
The compass is the tool of applied thought, while the ruler and the square verify its traced lines. Medieval images often show God creating the world using a compass. The compass was considered a cosmological symbol because it can be used to measure as well as to generate a perfect circle, hence it symbolized dynamic creation. Turning around its point, it also represented the cycle of existence. In fact, the circle created by the compass is the manifestation emanating from the initial point. This point is not only a symbol of creation, but also the initial point inside the human mind: consciousness.