A grappling hook is a climbing device, most commonly associated with movie characters stealthily gaining access to the roof of a building without notice or climbing over a wall. The hook features a metal tip with one or more extended teeth, which is tossed at the structure being scaled and hooked over a lip of the structure. A long rope is tied to the end of the metal tip and held onto by the climber. With the tip securely in place, the climber can then ascend the rope to reach the top of the structure.
Place one shelf bracket over another bracket and secure in place with wire, then repeat with the remaining brackets so you have two pairs of brackets. Secure the brackets with the wire by passing wire through one hole designed for a mounting screw on both brackets, then back through an adjacent hole, and tying the wire tight against the brackets. Repeat this for a pair of holes near the bottom of the brackets, near the end of the top of the brackets and near the bend in the brackets.
Position the brackets next to each other so that the angle between the top arms creates approximately a 45-degree angle. Position the wood dowel between the backs of the pairs of brackets, then bind the brackets in place using metal wire.
Tie a piece of metal wire through the bottom mounting hole in each or the brackets so that there is a loop approximately 1 inch in diameter beneath the bottom of the brackets.
Wrap the brackets in duct tape. Wrap around the bracket assembly, starting just above the loop, and continuing to the end of the top sides of the brackets. Wrap around the entire assembly at least twice, as more tape applied will give extra support to the brackets.
Fold the rope in half, then pass both ends of the rope through the loop in the bottom of the mounting bracket and the loop caused by folding the rope in half, then pull tight. The rope is now secured to the hook, with two even lengths of rope extending down.
Tie a series of knots in the rope, approximately 1 to 2 feet apart, depending on your rope-climbing preferences. Use both pieces of rope held together like one piece in each knot. If a single knot is too small for your feet to get purchase, use double knots for a larger knot size.
Test the hook by placing it over a low lip and first pulling on the rope, then slowly lifting your legs until the hook is supporting all of your weight.
Do not attempt to climb dangerous heights with your hook without wearing proper safety equipment such as a climbing harness.