This is the skill of drawing well — not a quick doodle, but a sure hand with lines and shape, whether you are making a picture or a careful plan of a building. The person who does that work, especially plans and technical drawings, is a draughtsman; draughtsmanship is the craft itself. Though actually, people also use it for fine art, not only for blueprints. It is a rather formal British word, a little old-fashioned, and you would not use it for a child's sketch unless you were being kind or a little grand. In American English the same idea is usually spelled draftsmanship.