Tire clamp is my guess.

[moparthug]

I just picked up a pair of these clamps, they sure look like tire repair, but the name is throwing me off. Mayo Radiator, Oakland Ca. Too big for tube repair, a tire clamp of some sort, 1920's-30's?

[Papaw]

Maybe for holding the head cap on a radiator core while soldering?

[moparthug]

Oh, I hadn't thought of that, perhaps they are radiator tools.

[oldgoaly]

maybe 2 of them could hold the tanks (top & bottom) to the core
johnson sells radiator tools and supplies
http://www.johnsonmfg.com/temp/FTOOL.HTM

[oldgoaly]

how they are used

[moparthug]

Thanks a bunch, info AND a picture, what else could I ask for?

[oldgoaly]

That picture was in my head on how they were used. It has to be a few years since I was on the Johnson or Barbee websites  checking autobody solder prices. It may have been "How it's Made" on making radiators that I saw it. Some how it stuck in my mind.