Precision is a military specialty. From drills to uniforms, each aspect of life in the U.S. Army is governed by specific, straightforward requirements. The U.S. Army Service Uniform website specifies the four-in-hand knot as the official knot of both casual and formal occasions in which army personnel wear neckties.
Four-in-Hand Knot
Rest the tie around your neck with the wide end hanging on your left, about twice as long as the narrow end.
Cross the wide end over the narrow end and to your right, under and back to the left, then finally over once more to the right.
Loop the wide end up through the hole underneath your neck.
Slide the wide end back down through the front loop of the knot and adjust as needed.
Tighten and adjust the knot as needed, remembering that it will always look slightly asymmetrical.