To make the clamp, cut four L-shaped clamping blocks from 3/4-in. pine and groove the outside edges of the blocks a little wider than the rope diameter. Then round, smooth, and wax the grooves to minimize friction. Cut or drill a circular area at the inside corner of the blocks to allow for slight inaccuracies (which accumulate at that point) and to permit excess glue to escape. When you’re ready to glue, place a piece of waxed paper under each block to prevent it from becoming glued to the frame.

For the rope, choose something with a little stretch. I use 1/8-in. nylon. Tie a loop in the rope just long enough so that it can barely be snapped over the blocks. This will hold the frame together while final adjustments are made in the glue joints. When the joints are right, twist a dowel onto the rope and turn it to produce whatever pressure is desired. The leverage is tremendous, so don’t overdo it. It’s a good idea to put a weight on the frame while you’re applying pressure. If one corner comes up a little, the whole assembly may twist and fly apart.

When the pressure is sufficient, tape or tie the dowel to the rope. Always maintain a tight grip on the dowel; it can unwind with surprising force.

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