Page 81 - Joseph B. Healy "The Pocket Guide to Fishing Knots"

Duncan Knot/Loop or Uni-Knot

1. Bring the tag end through the hook eye (or around a reel’s arbor). At
the end closest to the hook eye or the reel, begin wrapping the tag
around the standing line. Do this four or five times, each time
passing the tag end through the bottom loop.
2. Bring the tag one final time through the bottom loop, and then pull
the tag to tighten the knot, as shown here.

Duncan Knot