After stringing these beads onto wire, I realised that I had no suitable clasps left, so I made my own. I don't know what the conventional way to make an S clasp is. I took some 20 gauge craft wire and folded it in two to give the clasp some strength, leaving the middle where I folded it slightly open in order to attach it to a jump ring. I shaped it, and coiled the cut end. Then I hammered it flat in order to harden it a little.
I attached two large closed rings to the beadalon wire and crimped - one to fix to the clasp and the other to loop over the clasp.