1. Put the metal point of the compass on a corner of the square at point A.
2. The pencil point goes out to the opposite corner of the square--B.
3. Arc the compass down to C.
4. Draw a line extending the side of your square out and finish making a rectangle.
You now have 2 sizes to work with inside the whole piece. Instructions for finding additional dimensions to use within your orthogon are found at the Design Application link.
About Orthogons Orthogon Instructions Design Application Historical Use References Links Artist