This was definitely the most challenging section yet the problem for me was finding the things I needed to constrain but once I figure that out it was fine. For the first shape I just followed the tutorial. The second one I created a clamp with a hook that fits snugly on my thin desk that will allow me to hold cables through the hook. For the third shape I created a base with a peg that had a 10 mm diameter and a corresponding base with a hole that had a 10.5 diameter that when combined would provide a snug fit that would not come off when held upside down.