Especially when it comes to trying to truing up a 29" wheel with tire in a Park TS-2. It just don't work. With the tire, the wheel is too big for the truing caliper arms to get even remotely close to the rim. Oh sure, I could buy the handy extension arms Park conveniently now makes (and I probably will, eventually). But for a quick "I just want to touch up this wheel without having to remove the tire," I set up this little jig that involved a magnet and a 3mm hex wrench. Worked pretty darn good.
(What's playing: Elvis Costello and the Attractions Waiting for the End of the World)