Page 80 - Peter Randall "The Craft of the Knot.."

The Wagoner’s Hitch is a leveraged hitch very similar to the Trucker’s
Hitch. It needs tension on it to stay secure, and it comes undone with
just a shake.

STEP 1 Make a crossing turn, then grab a bight in the running end just
below it.

STEP 2 Pull the bight of the running end through the crossing turn.
This forms a lower loop that the running end will pass through after it
goes around an anchor point.