Here is how to string or “sew” hollow tubes to make a pair of tetrahedra which are joined at their bases.
Use a long wire or cord and begin with a tube at the orange “1” through orange tubes “2” and “3” then follow the sequence of blue tubes “4” through “6” and finally tubes “7” through “9.”
Catch or loop through the stringing thread as you go so that the doubled tetrahedron becomes three-dimensional.
Note that you start at the top and end at the bottom of each module so you can make a long string of them with one length of wire…
Doubtless, beaders already know this procedure to make fragile looking necklaces, earrings, or bracelets. Though I love beads, and will confess to having a nice collection of them, I have little experience with using them.
I had to see what was happening with novice eyes. My tubes here were about a foot long, made of thin black plastic—from The Scrap Box. If you look closely you will note that I used some wooden beads to catch and hold the doubled tetrahedra in three dimensions.
I made several “chains” of double tetrahedra. They were fun to manipulate into rings which could revolve into different shapes. I gave a couple of them away and wonder what has become of them. One became a trellis for a clematis which was planted at the base of the street sign in front of our house. The tubes were ridged but fragile so deteriorated after the first season.