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A hook is a tool consisting of a length of material, typically metal, that contains a portion that is curved/bent back or has a deeply grooved indentation, which serves to grab, latch or in any way attach itself onto another object. The hook's design allows traction forces to be relayed through the curved/indented portion to and from the proximal end of the hook, which is either a straight shaft (known as the hook's shank) or a ring (sometimes called the hook's "eye") for attachment to a thread, rope or chain, providing a reversible attachment between two objects.

In many cases, the distal end of the hook is sharply pointed to enable penetration into the target material, providing a firmer anchorage. Some hooks, particularly fish hooks, also have a barb, a backwards-pointed projection near the pointed end that functions as a secondary "mini-hook" to catch and trap surrounding material, ensuring that the hook point cannot be easily pulled back out once embedded in the target.

• Bagging hook, a large sickle or reaping hook used for harvesting grain^[1][2]
• Bondage hook, used in sexual bondage play
• Cabin hook, a hooked bar that engages into an eye screw, used on doors^[3][4]
• Cap hook, hat ornament of the 15th and 16th centuries
• Cargo hook, different types of hook systems for helicopters
• Crochet hook, used for crocheting thread or yarn
• Drapery hook, for hanging drapery
• Dress hook, fashion accessory
• Ear hook, to attach earrings
• Fish hook, used to catch fish
• Flesh-hook, used in cooking meat
• Grappling hook, a hook attached to a rope, designed to be thrown and snagged on a target
• Hook and chain coupler, mechanical part for the coupling for railway vehicles
• Hook (hand tool), also known as longshoreman's hook and bale hook, a tool used for securing and moving loads
• Hook-and-eye closure, a clothing fastener
• Hook-and-loop fastener, a type of textile fastener
• Hook hand, also called prosthesis, an artificial hand replacement made from a hook
• Lifting hook, for grabbing and lifting loads
• Mail hook, for grabbing mail bags without stopping a train
• Meat hook, for hanging up meat or carcasses of animals in butcheries and meat industry
• Prosthetic hook or transradial prosthesis, part of a prosthetic arm for amputees
• Purse hook, used to keep a woman's purse from touching the floor
• Shepherd's hook, a staff used in herding sheep or other animals
• Siege hook, an Ancient Roman weapon used to pull stones from a wall during a siege
• Tailhook, used by aircraft to snag cables in order to slow down more quickly

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