“Sign painters shade their letters to the lower left by default”
John Downer, interviewed in Sign Painters (p. 98):
In the sign trade, we use more capitals than we use lowercase, so the capital E is the most ubiquitous letter in traditional sign painting. You can shade that letter with four strokes if you shade to the lower left, but it takes eight if you shade to the lower right.
Sign Painters is in our library.