Collection of thoughts:

I will add and hopefully refine this list.

Construction lines (plumb lines)- lines that continue past their edges to help show the relationships to other shapes and lines.

Contour- Think “descriptive line”. Describe space without shading, just line quality. Intaglio, lines etched into metal plates, can show some great examples of how only line is used (though often they use it to create value by hatching and cross hatching)

Charcoal- can and should be fixed by a spray fixative. Hairspray works. Vine charcoal is excellent as an impermanent sketching tool, to be worked over. Because of it’s impermanence it is not good to be used for anything meant to be kept.

Keep in mind.

The key of this exercise is space. Try to understand it and then be able to portray it on your two dimensional surface.