The increasing power capabilities of crossbows -- some now have a draw weight of over 90 kg (200 lb) -- means most people aren't strong enough to cock a crossbow without some sort of mechanical advantage. Cocking ropes are easily stowed in the pocket of a jacket or pack. Making a cocking rope for a crossbow will reduce the amount force needed to cock the crossbow by 75 per cent.
Measure two 15 cm (6 inch) sections of wooden dowel and mark them with a pen. Cut the sections with a saw, creating two handles for the rope, and drill a hole through the centre of each handle.
Hook one end of an "s" hook into the eye of a pulley and crimp the hook closed around the eye with pliers. Repeat with another hook and pulley.
Insert one end of a rope, twice as long as the bow, through the hole in one of the wooden handles. Tie a half-hitch (granny knot) on the end of the rope so it will not pull back through the hole in the handle.
Thread the other end of the rope through the wheels on both pulleys and then through the hole in the second wooden handle. Tie the rope off, loosely, with a half hitch.
Hold the rope in the middle, allowing the rope to hang down in two equal sections, with the pulleys resting against the wooden handles. Place the point where you are holding the rope into the rope cocking groove on the back of the crossbow's receiver.
Place the cocking stirrup, at the front of the crossbow, against the ground. Insert your foot firmly into the stirrup, with the ball of your foot pinning the stirrup to the ground. Bend over and hook the open ends of the "s" hooks on to the bowstring, one hook on each side of the arrow rest.
Pull the rope, by the end with the loosely tied knot, through the hole in the handle, until the rope is taught. Pinch the rope at the handle with one hand and pull the hooks free from the string with the other hand. Tightly retie the knot in the rope at the point where you have the rope pinched between your fingers. This creates a custom fit for the cocker to the bow. Melt the ends of the rope with a match to seal the nylon strands and prevent fraying.
Reattach the cocker to the crossbow, grasp one handle in each hand and stand up, lifting with your legs and rolling your shoulders back. This should be enough to set the bowstring into the cocking latch, depending on your height. If not, lift the last 2.5 cm (1 inch) or so by pulling upwards with your arms. Be absolutely certain the safety lever snaps (automatically) into place before you release tension on the rope.
After you have used the cocker several times the rope will stretch slightly, possibly making it necessary for you to readjust (shorten) the length of the rope.