The ruler contained the “trait”, the chosen unity of measure. Square and ruler connect the points set out by the compass to form angles, triangles, squares, rectangles and other polygons. They materialize the ideas of the compass. While the compass represents “spirit”, the square represents “matter”. Indicating horizontality and verticality, the square symbolizes space. The compass, which evokes spirit because it draws curves, is regarded as active, while the square, related to matter, is regarded as passive.

The crossing of square and compass indicates a balance of two elements: spirit and matter. This crossing represents the two halves of the Hermetic Androgyne, the Rebis, in which the two principles of manifestation, heaven and earth, male and female, active and passive, sun and moon, spirituality and materiality, are united.

Tracing a plan was an act of meditation. In the Middle Ages, every created form in the context of a “sacred” building represented an idea or a human experience of the un-graspable, which surpass and baffle our rational minds. Building a cathedral was an expression of spirituality, not a spirituality losing itself in abstract and subjective conceptions without any link to reality, but a spirituality given concrete form and expressed in stone: applied spirituality.

Another tool was the rope with 13 knots, making 12 equal segments. With 12 segments, many geometric shapes can be formed, like circle, square, rectangle and three kinds of triangles: equilateral, isosceles, and scalene. Twelve is a number that can be divided evenly by 2, 3, 4, and 6. There are 12 months in the year. Each day is 24 hours long, two times twelve. There are 12 apostles, 12 tribes of Israel, 12 knights of the round table and 12 signs of the zodiac…