Versatackle knot
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A versatackle is a way of simulating a block and tackle without actual pulleys or deadeyes. It consists of two loops with the rope passed back and forth between them.
Step by Step Images
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Make a loop knot on one end of the rope and another loop knot in the middle, just longer than the area to be bound. (An overhand loop knot is used here)
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Pass the second working end through the loop knot in the first working end.
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Bring the second working end up through the loop knot tied in the middle of the rope.
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Repeat until there are three complete passes (three ropes in each loop).
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Pull on the second working end, and work out the slack to tighten.