Bob Thrun describes the H-Bar knot in his book Prusiking as "a semi-mechanical version of the Prusik knot," although in his illustration (reproduced here), the rope follows the path of a strap hitch (Ashley’s #1694). It works either way, sliding more easily than a prusik but not holding as well.
I made my H-Bars from 11 mm. and 6.6 mm. mild steel
(A36). The horizontal pieces were press fit to the vertical bars.
The original H-Bars were welded; I intend to weld mine someday
when I get my MIG unit working.
I decided that I placed the horizontal bars too far apart on Version A, so I moved them closer on Version B. I made the side bars longer to reduce the chance of the sling slipping off the H-Bar.
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