Finally made a video about what is likely the most difficult exercise in all my lessons. The form intersections from lesson 2 (http://drawabox.com/lesson/2). Here I go over some common mistakes and do a little demonstration.
If you're confused, read over the "Exercise" section of Part 3 on http://drawabox.com/lesson/2. There's more diagrams and written explanations. If you still don't quite understand, feel free to leave a question as a comment on the video.
Check out the other structured, exercise-based foundational drawing lessons at http://drawabox.com
Also, consider helping support us through Patreon, at http://patreon.com/uncomfortable
+ The explanation for that incorrect form intersection can be found here, http://www.reddit.com/r/ArtFundamenta..., by /u/Grieffon. If anyone else finds any mistakes in my videos (of which I am sure there are many), feel free to call me out.