Step 1: Form a bight near one end of the rope.

Step 2: Pass the tag end of this bight around the standing part of the rope and back through the bight, forming a large noose.

Step 3: Pass the tag end under and around the rope just ahead of, and then back up through, the bight.

Step 4: Tighten, but allow the running end of line to pass through the knot freely.