ABOUT THE HALF-WINDSOR KNOT
The Half Windsor knot is an extremely versatile knot. Unlike what the name suggests, the Half Windsor knot is actually closer to three-quarters the size of the Windsor knot. The Half Windsor is medium in size, nearly symmetrical and, when tied correctly, it produces a deep and substantial dimple. Best used with neckties of a medium to light thickness.
KNOT SIZE 3/5
THE HALF WINDSOR KNOT TYING INSTRUCTIONS
1. Start with the wide end of the tie on the right and the small end on the left. The tip of the small end should rest slightly above your belly-button (this will vary depending on your height and the length & thickness of your tie). Only move the active (wide) end.
2. Wide end over the small end to the left.
3. Under the small end and to the right.
4. Up to the center, towards neck loop.
5. Through the neck loop and to the left.
6. Across the front, over to the right.
7. Up into the neck loop from underneath.
8. Down through the loop you’ve just created in the front.
9. Tighten the knot by pulling down on the wide end. Slide the knot up & adjust.
SOURCE: THE GENTLEMANUAL