A grappling hook is a device with multiple hooks (known as claws or flukes), attached to a rope; it is thrown, dropped, sunk, projected, or fastened directly by hand to where at least one hook may catch and hold. Generally, grappling hooks are used to temporarily secure one end of a rope. They may also be used to dredge for submerged objects. Historically, grappling hooks were used in naval warfare to catch ship rigging so that it could be boarded.
A common design has a central shaft with a hole ("eye") at the shaft base to attach the rope, and three equally spaced hooks at the end, arranged that at least one is likely to catch on some protuberance of the target. Some modern designs feature folding hooks to resist unwanted attachment. Most grappling hooks are thrown by hand, but some used in rescue work are propelled by compressed air (e.g., the Plumett AL-52), mortar or a rocket.
Grappling hooks are used by combat engineers breaching tactical obstacles. The grappling hook is launched in front of an obstacle and dragged backwards to detonate trip-wire-fused land mines, and can be hooked on wire obstacles and pulled to set off booby traps on the wire. Two tools are available for this purpose; the rifle-launched grapnel, a single-use grappling hook placed on the end of an M4/M16 rifle, or the crossbow launched version. A grapple can clear up to 99% of the trip-wires in a single pass.
RAIDS, Rifle Actuated IED Defeat System, a reusable grappling hook was developed in 2011 by Cardinal Scientific Inc. The first grappling hook to be reusable using live ammunition, the tines are interchangeable and are manufactured from different materials to locate IED's in a variety of terrain, foliage, and depth of soil penetration. The system was designed to designate and defeat Command Wires, Pressure Pads, and Tripwires and provide remote delivery of other payloads. Replaceable bullet traps give the operator 10+ shots with live penetrator ammo. Used by dismounted troops, SWAT, and Bomb Disposal Units to engage threats at range or a safe stand-off distance.
A significant development of the grappling hook is the subject of British Patent GB2471340, invented by John G. Williams.The product, known as Line-A-Sure, is composed of non-metallic materials which permit the grappling hook to be used where damage to personnel and property might occur with the normal metal ones. It is intended for use as a mooring system for boats, although its uses are wider. The unique features are that its flukes consist of parabolic curves that enable the force transmitted from the rope to be taken up gradually. The polymeric materials of construction extend the mode by which the grappling hook works from the normal wedging and entanglement. The surface of the flukes has give, and this permits improved attachment by allowing temporary deformation, and readjustment of the surface deformation. The device also floats enabling the mariner to pick up moorings, and retrieve floating objects. The shaft consists of sprung materials that flex to enable the load to be taken with minimum jerking, which again assists the mariner.