What kind of drawing line shows the ridges and edges of an object?

A contour line is the line that shows the ridges and edges of objects and figures in drawings. Contour lines are used to create boundaries that divide one area from another, show changes of a plane within the object and define the outermost edges of a form.

Contour line drawings are similar to coloring book pages where value (shadows or highlights) and texture (visual feel of a two-dimensional work) are not present, and only the contour edges of the shapes, values and textures are there. Mastering the art of contour line drawing is a good foundation for drawing beginners and is typically considered a vital skill for cartoonists.