Abstract
Lorenz Lechler, "Baumeister" in Heidelberg in the later Middle Ages, writes "Unterweisung" for his son. This paper analyzed the design method of the templates of the architectural elements in this book. He instructs to design the templates of two sizes-"alt" (old, large) and "jung" (young, small)-as in the ratio 7 : 5 by the following means : (1) The scheme consisted three inscribed squares that has the sides as in the ratio 10 : 7 : 5. (2) Two scales that is in the ratio 7 : 5.
