I couldn’t draw myself out of the error I made with the tilt of the man’s head, in the drawing below. But I could, with shading. At first I drew the head with the chin jutting out. In fact, it was tucked in. I darkened the line of the correctly-drawn chin, but I had to do more. The two chins had equal value and given that erasure was not an option, I haloed the head with shading.

Seated Man and Mistake Rectified by Parallel Lines
Pen and Ink Sketch
10″x8″ 111# Moleskin Journal