This book, by first time, discovers the meaning and function of the stonemason's signs. Nine years of research, 96 churches, 67.310 signs more than 50.000 photos form the basis of this book. The first part justifies that from a total of 60 different signs the most important come from Trinitarian’s Chrismon in which P represents the Father, the + and X the Son, S the Holy Spirit, A the Alpha and ω the Omega. To which must be added the stonemason's tools, L the square and ˄ the compass and the star for Mary. These signs represent 70% of the 67,310 signs. It also justifies the existence of a signs plan linked in each church to the owner institution and the advocation of the temple. The second part starts with a global excel of all churches and signs with their totals, it continues with 24 tabs. Each tab presents the sign, its meaning and its justification. The third part presents each church with its ground plan, with an Excel with the predominant signs by zones and comments on them.