The interest of the initiators of the Guédelon project did not relate to a finished castle but to the process of its construction. However, building a castle today on a model and in the manner of the 13th century is a daring bet. The archives of construction sites are scarce for this time, and the little that has been transmitted (chronicles, charters, construction accounts, etc.) does not reveal much about the trades or their techniques. It was, therefore, necessary to observe the many buildings of the Middle Ages and learn how to decipher them and draw inspiration from their structures.