I made myself Spurlock-style key clamps, from his plans in articles. He started out using backrail cloth on them, and it has worked fine for me. I put it on with Elmer's.
I don't know if my car gets up to Mississippi heat standards, but they have lasted in a hot car just fine.
The first set had two thumbscrews, with the machine screws able to swing out of slots at the ends of the clamps, but then I saw that his newer type had another one in the middle. With just two screws, one at each end, the clamps tended to bow in the middle, so they worked better after I added a third.
I used 2x2" cedar banister blanks bought at a woodworking store. I added some nylon cords so they could both be picked up to carry at once. They've served me well for many years.
Terry, you make me glad that I made my own, from wood, and the nylon ropes I installed simply had knots on the ends, nested in holes through the wood.
Great minds thinking alike, Lar.
Aside from adding the third machine bolt and thumb screw in the middle, and the carrying cords, I also took a small soldering iron and put my last name with a little mountain outline (being from Colorado) on the top. Around my immediate area, anyone who has anything to do with pianos will know my last name. And I made marks across the ends of both halves, different for the two sets, so I don't try to swap them by putting the wrong top with the other base. They are not interchangeable because the middle bolt is not in quite the same place.
They seems just as good as when I made them, despite a lot of use. It seems they may outlast me. Hopefully they and my other tools and supplies can find some younger piano techs when I no longer am likely to use them, which is not yet, thank heavens and Pfizer.
I'll try to take some photos of mine.