To assemble the jumpers, I threaded a bare wire end through each spring and pair of holes. The end of the stripped wire was wrapped around the portion going into the first hole, to secure the assembly. (I was careful, though, to keep the bare wire from making contact with the springs.)
I've found that my homemade jumpers work fine in all but the tightest spots. And better still, the insulating quality of the dry wood prevents shocks!