The reach of most bar clamps is limited to just a few inches. So when a clamping task comes along that’s beyond this, you’re usually left scratching your head. The solution is to have a set of these deep-reach clamps hanging on your clamp rack.
Think of it as a cross between a C-clamp and an old-fashioned handscrew. Long, stout, jaws apply clamping force nearly a foot away from the edge. I chose straight-grained hard maple for the jaws for the most strength.
The mechanism consists of hardware-store items: a carriage bolt, washer, and coupling nut. I used 1/2" hardware to stand up to heavy use. The jaws are linked at the back end by a surface-mounted hinge. In use, the back end of the jaws are pressed together, so there isn’t much stress placed on the hinge or its screws.
The two jaws of the clamp are nearly identical. The only difference is the upper jaw has a slot (rather than a hole) to accept the carriage bolt. Drill the hole and create the slot before cutting the jaws to final shape. I opted for a maple handle and coupling nut to keep the cost down and match the jaws.