There is evidence that during the Carthaginian invasions of Greece in c. 2200 B.C., they used metal handcuffs to restrain their Greek captives. The English word "handcuff" comes from "handcop." (To "cop" means to "capture" or "get a hold of." Thus, the term "cop" for policeman.)
There are two distinct subtypes of contemporary metal handcuffs: one in which the cuffs are held together by a short chain, and another, of more recent origin, which uses a hinge for this purpose. Since the hinged handcuffs are somewhat smaller when fully extended they are seen as being more easily utilized by a police officer who has relatively small hands, and are also regarded by some observers as more secure because the wrists end up being held closer together than with the chain subtype, and are also bound more rigidly. A third type, the rigid handcuff, has a metal block or bar between the cuffs. Whilst bulkier to carry it permits several variations in cuffing and, with one hand cuffed, can be used in control and restraint techniques. Various accessories are available to improve the security or increase the rigidity of handcuffs, including boxes that fit over the chain or hinge and can themselves be locked with a padlock.
Sometimes two pairs of handcuffs are needed to restrain a person with an exceptionally large waistline because the hands cannot be brought close enough together; in this case, one cuff on one pair of handcuffs is handcuffed to one of the cuffs on the other pair, and then the remaining open handcuff on each pair is applied to the person's wrists. Oversized handcuffs are available from a number of manufacturers, as are juvenile-sized restraints, though none of the latter in current production are approved for use by the United States National Institute of Justice.
On occasions when a suspect exhibits extremely aggressive behavior, leg irons may be used as well; sometimes the chain connecting the leg irons to one another is looped around the chain of the handcuffs, and then the leg irons are applied, resulting in the person being "hog-tied". In a few rare cases, hog-tied persons lying on their stomachs have died from positional asphyxia, making the practice highly controversial, and leading to its being severely restricted, or even completely banned, in many localities.
In the past, police officers typically handcuffed arrested persons with their hands in front of them, but since approximately the mid-1960s behind-the-back handcuffing has been the standard. The vast majority of police academies in the United States today also teach their recruits to apply handcuffs so that the palms of the suspect's hands face outward after the handcuffs are applied; the Jacksonville, Florida Police Department and the Los Angeles County Sheriff's Department are notable exceptions, as they favor palms-together handcuffing. In addition, suspects are handcuffed with the keyholes facing up (away from the hands) to make it difficult to open them even with a key or improvised pick.
There are ways of escaping from handcuffs:
The above methods are often used in escapology. As most people's hands are larger than their wrists, the first method was much easier before the invention of modern ratchet cuffs, which can be adjusted to a variety of sizes. Modern handcuffs are generally ratcheted until they are too tight to be slipped off the hands. However, slipping out of ratchet cuffs is still possible. During his shows, Harry Houdini was frequently secured with multiple pairs of handcuffs. Any pair that was too difficult to be picked was placed on his upper arms. Being very muscular, his upper arms were far larger than his hands. Once he had picked the locks on the lower pairs of handcuffs, the upper pair could simply be slipped off.
It is also technically possible to break free from handcuffs by applying massive amounts of force from one's arms to cause the device to split open or loosen enough to squeeze one's hands through, however this takes exceptional strength (especially with handcuffs made of steel). This also puts an immense amount of pressure on the biceps and triceps muscles, and when tried by suspects (even unsuccessfully) can lead to injury, including bruising around the wrists, or tearing the muscles used (including dislocating them from the bone itself).
Another common method of escaping (or attempting to escape) from being handcuffed behind the back, is that one would, from a sitting or lying position, bring one's legs up as high upon one's torso as possible, then push one's arms down to bring the handcuffs below one's feet, finally pulling the handcuffs up using one's arms to the front of one's body. This can lead to awkward or painful positions depending on how the handcuffs were applied, and typically requires a good amount of flexibility. It can also be done from a standing position, where, with some degree of effort, the handcuffed hands are slid around the hips and down the buttocks to the feet; then sliding each foot up and over the cuffs. These maneuvers, and the reverse (otherwise impossible) maneuver of bringing the handcuffed hands up behind the back and forwards over the head and then down in front, can be done fairly easily by some people who were born without collarbones because of the inherited deformity called cleidocranial dysostosis.
Police handcuffs are sometimes used in sexual bondage and BDSM activities. This is potentially unsafe, because they were not designed for this purpose, and their use can result in nerve or other tissue damage; bondage cuffs were designed specifically for this application.