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I set masonry and tracery out by hand, with full size drawings in a traditional fashion. This helps me to understand the window to be repaired, and to even replicate mistakes in the original drawing that produced the window. So any new tracery stones will fit the old window. I can also adjust the new masonry to suit any movement in the structure of the window.

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Auto cad drawing systems are fine in their place, but the fact that they produce a drawing that is so correct, makes it a liability where repairing ancient buildings, with unique problems.