To cart lumber atop your vehicle, the trucker's hitch is the knot to know. Start by tying off one end of the rope to your roof rack's crossbar. Next, sling the loose lead over the load to be lashed down and make an overhand midline loop. Wrap the free end of the rope around the crossbar, then thread it through the eye of the loop. This will create an improvised pulley, allowing you to tighten down the load. Once you get it snug, wrap the end twice around the rack's side rail to maintain tension on the line, and secure using two half hitches with a quick release slipknot.