This on-the-spot sketch from the early 1980s was made with a brush pen on drawing paper. Everything in shadow goes to black, and everything in light goes to white, ignoring the contour lines bounding the light side.
The technique is a good way to simplify detail. Each figure is an edge-lit silhouette. I worked from left to right, completing each man before starting the next, because I anticipated that the subjects might come and go unexpectedly.
Related posts: high-contrast shapewelding, edge lighting, two values