Several years ago I became interested in mathematical knot theory, so I got a book called The Knot Book by Adams. I also got the Ashley Book of Knots by Clifford Ashley, which is a 600-page encyclopedia of actual knots in ropes/string/etc. I’d forgotten about both books until last night, when a key plastic piece on our bedroom blinds broke: the part that joins the lower single cord to the upper multiple cords that actually go to the blinds.
I whipped out the Ashley Book and found the perfect bend, #1463, which is good for joining two cords that have different thickness. I’ve shown my results below, but note that the actual knot is in the upper left and the rest of it is just my quick work to make sure that the thicker piece stays bent and doesn’t straighten out and try to pull through. I don’t think Ashley would approve of that part.
Thinkinator 