20th February: Handcuff Day

Today is Handcuff Day. How much do you know about handcuffs?

1. Why is it handcuff day on 20th February? Because it was on this date in 1912 that the common swing bow ratchet handcuff was patented by George A. Carney. These were lighter and easier to carry around than the bulky models available before.
2. Handcuffs are made from various metals, including carbon steel, stainless steel and aluminium, or from synthetic polymers.
3. Disposable plastic cuffs which resemble cable ties can be carried in large quantities and are used by soldiers and police in riot situations. Airlines have them, too, to restrain passengers who get out of hand. They have their drawbacks, however. Cuffs like this can't be loosened and the only way to remove them is to cut them off. Hence if someone is kept in custody for a while, they might go through several of them as they need to be removed for fingerprinting or if the person needs to use the bathroom.
4. Most handcuffs in the UK, USA and Canada can be opened with a universal key. Maximum security handcuffs require special keys, however, so even if you could get hold of a key it's not guaranteed you could bust your friend out with it!
5. This is one of the reasons escapologists often use handcuffs in their acts, because one way of escaping is to have a key hidden somewhere on their person. Because they are temporary restraints, handcuff locks aren't all that complicated, so they can be picked relatively easily using a lockpick (the practice of many police forces of handcuffing people with their hands behind their backs, palms facing out and the keyhole on top is to stop people from doing this).
6. In the US, there are models of handcuff key that fit behind a police officer's badge. These are sometimes called "the New York tuning fork".
7. Handcuffing people doesn't come without risks. People use their hands to break falls, so being handcuffed increases the risk of injury from a fall, for which the police officer would be liable - so they have to be ready to catch a handcuffed prisoner if they stumble.
8. If handcuffs are too tight and/or left on too long there is a risk the prisoner will get handcuff neuropathy. Handcuff neuropathy is a colloquial name for Cheiralgia paraesthetica, or Wartenberg's syndrome, a condition caused by compression or trauma to the superficial branch of the radial nerve, usually due to constriction of the wrist. Symptoms include numbness, tingling, burning or pain. A person can also get it from wearing a tight wristwatch or bracelet.
9. In some parts of the world, such as Japan, France and Hong Kong, it is illegal to photograph suspects being carted away in handcuffs for use on TV or in the papers. This is because being cuffed implies guilt and could prejudice the trial. A Japanese man called Kazuyoshi Miura argued this in court, and was successful. So in Japan, handcuffed hands are pixelated. In France, the pictures cannot be used at all, and in Hong Kong the suspect is given the option of wearing a black cloth bag over their head.
10. Of course, we have to mention the kinky stuff. If using handcuffs for bondage, police handcuffs aren't suitable because they are potentially unsafe, particularly because of handcuff neuropathy (see above). So there are special handcuffs for this purpose, similar to the ones used for restraining psychiatric patients, which have soft restraints.