Some of the architectural drawings date from the Middle Ages and are on paper 15 ft long and too fragile to handle. Laser measurements of the ancient cathedral have now been made so that a digital 3-dimensional virtual model of the cathedral now exists in its computers, and detailed modern plans can be output at will. When weathered stonework needs to be repaired or replaced, the computerized system can create life-sized models to guide the nine full-time stonemasons on staff in the on-site workshops against the north wall of the cathedral.