In the west front of the cathedral

In the west front of the cathedral, nearly fitted into one of the towers, was a work room for the master mason. Caris reached it by climbing a narrow spiral staircase in a buttress of the tower. It was a wide room, well lit by tall lancet windows. All along one wall were stacked the beautiful shaped wooden templates used by the original cathedral stone cavers, carefully preserved and used now for repairs.
Underfoot was the tracing floor. The floorboards were covered with a layer of plaster, and the original master mason, Jack the builder, had scratched his plans in the mortar with iron drawing instruments. The marks thus made where white at first, but they faded over time, and new drawings could be scratched on top of the old. When there were so many designs that it became hard to tell the new from the old, a fresh layer of plaster was laid on top, and the process began again.
Parchment, the thin leather on which the monks copied out the books of the Bible, was much too expensive to be used for drawings. In Cari’s lifetime a new writing material had appeared, paper, but it came from the Arabs, so monks rejected it as a heathen Muslim invention. Anyway, it had to be imported from Italy and was no cheaper than parchment. And the tracing floor had another advantage: a carpenter could lay a piece of wood on the floor. On top of the drawing, and carve his template exactly to the lines drawn by the master mason..
Merthin was kneeling on the floor carving a piece of oak in accordance with the drawing, but he was not making a template. He was carving a cog wheel with sixteen teeth. On the floor close by was another, smaller wheel, and Merthin stopped carving for a moment to put the two together and see how well they fitted. Caris had seen such cogs, or gears, in water mills, connecting the mill paddle to the grindstone.
He must have heard her footsteps on the stone staircase, but he was so absorbed in his work to glance up. She regarded him for a second, anger competing with love in her heart. He had the look of total concentration that she knew so well: his slight body bent over his work, his strong hands and dexterous fingers making fine adjustments, his face immobile, his gaze unswavering. He had the perfect grave of a young deer bending its head to drink from a stream. This was what a man looked like, she thought , when he was doing what he was born to do. He was in a state like happiness, but more profound. He was fulfilling his destiny
From the book ‘World without end’ by Ken Follet