A grapnel is a kind of many-pronged anchor. It's primarily used with smaller ships. Its lightweight and multi-pronged design has allowed it to be adapted for several other uses as well. The word "grapnel" is thought to have its origin in the French word "grapin," or "hook." It can have the alternative spelling of "grapple," or "grappling hook."
The anchor can have as few as three or as many as six prongs called "flukes." These flukes curve backward, somewhat like the half-open ribs of an umbrella, and can have sharp tips. By contrast, other styles of anchors are simply round weights or have only two large, flat flukes.
Due to its multiple flukes, a grapnel doesn't need to be carefully aimed when tossed in the water, but will be in the right position to hook onto almost anything. It works best around rocks or reefs, since the sharp prongs won't be able to gain a foothold in mud or silt.
The grapnel's light weight makes it a type of temporary anchor. In order for a ship to be so firmly anchored that it can stay moored even in storms, a much heavier anchor that can stand more than twice the weight of the ship will need to be used. One of the drawbacks of using a grapnel anchor is that sometimes it can get hooked so firmly into something that it is difficult to remove.
This type of anchor is normally used with smaller boats, such as fishing boats. It can also be used to dredge the bottom of a river for objects or to retrieve things floating by the side of a boat. During the early days of naval warfare, grapnels would be flung into the rigging of rival ships in order to facilitate boarding.
Some modern grapnels are made so that their prongs fold up. They can be locked in place at different angles for different conditions. They can also be folded shut for easy storage on the boat when not in use. Some modern grapnels avoid having sharp edges on their prongs in order to avoid possible accidents.
The basic design has also been used on a small scale for other tools which have nothing to do with ships. Miniature grappling hooks, when launched with special rifles, can be dragged by their attached ropes through areas to set off land mines. Several comic book heroes have also made grappling hooks part of their arsenal.