Sally's architectural challenge (another version here, I took this photo while waiting for the library to open:
Back home, I played with it. Some examples:
(I used the blue and turquoise to ensure I got the structure I wanted. All of the above are completely reversible)
The fat yarn could be, well, a fat yarn, or a bunch of finer yarns bundled together.
My idea is a lot less thought-about than Sally's, though...
I left the piece of wall for another day. It is a sort-of-cousin to the "damask fence" - maybe they can be used together?