How monuments such as Wells Cathedral or York Minster were conceived and built will always excite wonder, but for the first time this book presents newly discovered clues based on some of the builders' drawings. It also offers a long view of craftsmen's drawing techniques over five centuries. Several of the discovered drawings are on plaster tracing floors or on walls, but drawings on parchment and paper are also considered. The author also investigates the drawing techniques of carpenters and wood-carvers. He shows that the medieval drawing techniques continued in use after the end of the Middle Ages, and demonstrates how craftsmen working for Christopher Wren used some of the old techniques. This is a work of major importance for all architectural historians and medieval historians.