I've love shank buttons, especially old vintage ones. Unfortunately I find them difficult to use in jewelry because they tend to dangle or hang the way they want rather than the way I want.Just fooling around tonight I figured out that they could be turned into hook clasps, here are the steps I took:
I used 20 gauge annealed steel wire.
Slip the doubled wire through the shank of your button, I like a nice snug fit but I think it's ok if it wiggles a little bit.
Taking the short end , curl it up and around the shank with needle nose pliers, cut off any extra wire. This locks it in place and prevents the button from moving up or down.
With the remaining wire make the hook clasp.