Handcuffs

Handcuffs are locking restraints worn around the wrists to restrict movement. Most modern designs use two hinged or linked cuffs that ratchet closed and open with a key.

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Ratchet: A mechanism that permits motion in one direction while resisting motion in the other. Teeth on the moving bow engage a pawl to tighten a cuff while resisting its release.
Wrist: The joint connecting the hand to the forearm, formed by the distal radius and ulna and the carpal bones. The cuff surrounds this joint, where bones, tendons, vessels, and nerves lie close to the skin.
Police use of force: The physical force law-enforcement officers use to control situations or people. Applying handcuffs is a use of force whose necessity and proportionality may be assessed.
Handcuff neuropathy: Nerve injury caused by pressure from handcuffs, often affecting sensation or movement in the hands. Compression of superficial wrist nerves can cause lasting numbness, pain, or weakness.
Plastic handcuffs: Disposable restraints made from strong flexible plastic straps that tighten around the wrists. They offer a lightweight alternative to reusable metal cuffs but are generally cut off rather than unlocked.
Warded lock: A lock that uses fixed obstructions to block keys with the wrong shape. Many handcuff keys use a simple warded mechanism to turn the lock and release the ratchet.
Hinge: A jointed connection that allows two parts to rotate relative to each other. Hinged handcuffs connect the two cuffs with less flexibility than a chain.
Arrest: The legal taking of a person into custody under authority of law. Police commonly use handcuffs during arrest to limit movement and reduce escape risk.
Positional asphyxia: Life-threatening impairment of breathing caused by body position or restraint. Restraint practices can become dangerous when body position restricts breathing.
Thumbcuff: A restraint designed to secure a person's thumbs rather than the wrists. Its smaller contact area and different placement distinguish it from wrist cuffs.