The two half-hitches is a type of knot, specifically a binding knot or hitch knot. It consists of an overhand knot tied around a post, followed by a half-hitch. Equivalently, it consists of a half-turn around a post followed by a clove hitch of the running end around the standing part.

This knot is also sometimes referred to as a clove hitch over itself, or double half-hitch.

Two half hitches is the commonest of all hitches for mooring in particular and also for general utility. Steel gives the name in 1794. The difference between two half hitches and the clove hitch is that the former, after a single turn around a spar, is made fast around its own standing part, while the latter is tied directly around the spar.— The Ashley Book of Knots

Three-step process for tying the two half-hitches.

1. Begin by forming a clockwise loop around the pole, with the working end of the rope on top. Bring the working end through the loop. At this point, you have an overhand knot around the pole.
2. Bring the working end down and to the left. Loop it under the standing end.
3. Pull the working end through the loop just formed, tighten, and slide the knot along the standing end up to the post.

A correctly tied two half hitches resembles a clove hitch tied around the standing end of the line, not a cow hitch.