Ok. These are contour tubes. Contour lines are apparently very important for drawing things like trains, planes, and automobiles. As well as trees, people, clouds….the list goes on and on. Now I’m not seeing it because these are just tubes and don’t look anything like any of the aforementioned. However, I’ll take Marks word for it and trust all will be explained in time. My first one sucked. I was following my tendency to rush, so I really slowed down on the second one and I think it came out better.