As the name implies, this collar is made of metal links and is designed to control your dog by tightening around your dog’s neck. It is supposed to sit high up on the dog’s neck just behind their ears.
As there is no way to control how much the choke chain tightens, so it’s possible to choke or strangle your dog. It can also cause other problems, too, such as injuries to the trachea and esophagus, injuries to blood vessels in the eyes, neck sprains, nerve damage, fainting, transient paralysis and even death. It is best for your dog if you avoid using a choke chain.
More humane collars and good obedience training should make it unnecessary to resort to this aversive collar. If you insist on using one, consult an experienced trainer to learn how to properly size, fit, and use it. And never leave a choke chain on your dog as their regular collar; the chain could catch on something and choke your dog!