In the Middle Ages, each stonemason and quarryman had a distinctive sign that he engraved on one side of the stone he had cut. The symbols used included geometric figures (triangles, pentagons, etc.), work instruments (picks, hammers, etc.), crosses, letters, the workers' initials, etc. These marks notably enabled the construction site managers to check the quality of the work of the stonemasons employed on the task ('tâcherons') and to count the number of stones squared. Most of these signatures were engraved on the inner face of the stone and were not discovered until the destruction of the walls.