I've concluded that the WH1601-E6A transformer in a light fixture has expired, and ordered a replacement. The 12v wires coming out of the transformer are wired as follows: there a crimp-ons on the ends of the 12V wires, and these slide into spaces where a hex-keyed screw clamps down on them. I'm assuming I should repeat thjs by finding some corresponding crimp fittings; the alternative would be to cut and splice the existing wires to the wires coming out of the old transformer.
You should be able to find a good assortment of the crimp on terminals at any hardware or auto parts store. From your description it sounds like your terminal looks like this:
If you do not have the appropriate tool to crimp the terminals onto the wire you can purchase one at the same location that you get the terminals. A low cost crimp tool will likely look very similar to: