The Slip Knot Trucker’s Hitch is easy to learn, and we’ve found at least one use for it on every trip we’ve taken in recent memory.
The knot basically works like a ratchet strap. It can be used to affix boats, skis, or other gear to the roof of a car, or to tighten down guylines for a tent.
1. Imagine that the standing part of the rope (out of the photograph to the top) has already been tied to a fixed point on the opposite side of the vehicle with a bowline.
The rope has then been thrown over the load and we’re about to tie down on this side. Begin with an overhand crossing turn.
2. Make a bight just below the crossing turn and pass it through from back to front.
3. Pull down on the bight to complete a Slipped Overhand Knot. This provides purchase—a point where mechanical advantage can be exerted, much like on a pulley.
4. Bring the working end around the attachment point on the near side of the vehicle, then thread it through the drawloop of the Slipped Overhand Knot.
5. Haul down hard on the working end, then tie it to itself between the Slipped Overhand Knot and the attachment point using a Taut Line Hitch.
Step-by-step directions from The Field Guide to Knots by Bob Holtzman.