This clamp is a bit unusual, but it works very nicely. It is called a Lever Clamp, by Maple Tree Clamp CO. I got it about 20 years ago at a WW show.
It was advertised mainly as a drill press clamp, but useful for other tools. The company didn't last long, and I do not know if anyone else is making them.
You can vary the pressure very easily, and it is simple to use. The 2X4 is used as a spacer to allow the clamp to reach the work. It will clamp very tightly, but works well with just moderate pressure.
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