[RipNC]

To lever the two opposing wrenches together (so they are going opposite directions). I took a piece of rope and ran it thru each box end of the two wrenches, I was able to make 3 loops and then drew the loops taught and tied the two ends (simple square knot). Now having three loops I inserted my lever (I used a wooden handled hammer) between the loops (so 3 lines on either side of my lever). Then I simple turned the hammer to twist the lines which in turn shortened the loops drawing the 2 wrenches together. This creates a lot of tension on the line so a good strong line is important (thickness isn't important except that thicker line requires less turns to tighten it).

I found a photo of one (single loop) being used in a boat building project (much easier to visualise than the pic Beth shot while I was working it):