Handcuffs are restraint devices designed to secure an individual's wrists close together. They comprise two halves, linked together by a chain, hinge or in the case of rigid cuffs, a bar. Each half has a rotating part which engages with a ratchet which is closed around a person's wrist. Without the key, the person cannot move their wrists more than a few centimetres/inches apart, making many tasks difficult or impossible. This is usually done to prevent suspected criminals from escaping police custody.
I recommand only double lock handcuff. Those can block the moving part, this way less chance to hurt some one.
if you thing you know all models. see this link. http://www.ushandcuffs.com/Quickindex.html