Fill a small canvas or leather bag with sand or corn meal to about two-thirds of its capacity. Once filled, the ball should weigh about 1 to 2 lbs.
Tie the remainder of the bag into a tight knot, creating a snug ball of tightly packed filler below the knot and the neck of the bag above it.
Poke between four and six holes around the neck of the bag with a knife.
Thread the end of a rope through the holes that you cut in the neck of the bag, bringing the end of that rope back to the main line of the rope. Tie the rope off into a knot here, securing the rope to the neck of the bag.