The link wouldn't work for me, but >
http://www.hensleymfg.com/hensley_accessories.htm< did bring up a short animation of something I don't understand. Looks like the jack stand shaft is sliding back and forth across a flat rock (!!)
Instead of anything elaborate, I went to Radio Shack (WalMart, Home Depot, Lowe's, ...) and bought a couple small magnets for a few pennies. The ones I got are about an inch square and a quarter inch thick. There are round ones, too. They have a small hole in the center. I unfolded a wire coat hanger, and cut off two straight pieces of wire about 12" long. Put the magnets on a piece of waxed paper, filled the little hole with epoxy, jabbed the end of the wires into the wet epoxy, and let dry.
In use, I clack one magnet onto the hitch just forward of the ball, and the other onto the top of the coupler, with the wires pointing up. I open the tailgate on my Explorer, and from the driver's seat, I can see both wires. Just back up until the two wires meet, and bingo - I'm there.
Mighty simple, mighty cheap, and quite effective with any tow vehicle that lets you see the wires.
Bill