Cross-contour uses line to repeatedly trace the interior surfaces of an object. Unlike the edge contour, which usually flattens an object, repeated "cross sections" drawn inside the shape can create a convincing sense of dimensionality. The pencil is made to move across the paper as if it were actually touching the object, following the bumps and dips of the form. Cross-hatching involves adding a series of lines drawn at an angle to the cross-contour lines, creating areas of darker value. Additional layers of cross-hatching can be added until the desired tonality is achieved.
