![Countor Drawing](https://openlab.citytech.cuny.edu/elozano-eportfolio/files/2015/05/IMG_9059-300x224.jpg)
Cross-contours lines describe form and volume. These lines move around and across object as well through the object. This makes the object a feel of 3D showing edges and surface.
It reminds me of topographical map in which the lines move across the terrain. Cross-contour lines do the same thing.