Pipe clamps! Not for clamping pipes, but for using pipes to clamp with! They're each about 5 1/2 feet (168cm) long.
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I don't know much about these. I think they were just sold as clamp ends, you provided the pipe yourself. Dad repurposed the legs of an old swingset - you can see the boltholes. The adjustable side of the clamp threads onto the end of the pipe, the other clamp side moves freely when the trigger is pulled.
Not sure if Dad tapped the ends of the pipe himself, had somebody else do it, or they were already conveniently threaded exactly as needed.
It's more flexy than I'd expect an equivalent length of metal plumbing to be, but it seems to be capable of enough clamping pressure for woodworking purposes since Dad kept these around for so long. Makes sense - the legs had to be strong enough to endure a bunch of kids trying their darndest to launch into space.
Not sure how to clean this up. The clamp ends look well-weathered but all parts still move smoothly. As nasty as the pipe looks the rust doesn't seem to have gone deep. New paint is just gonna get scraped off, and I don't have the means to give it another coat of enamel.