Choke chains (also called choke collars, slip chains, check collars, or training collars) are a length of chain with rings at either end such that the collar can be formed into a loop that slips over the dogs head and rests around the top of the dog’s neck, just behind the ears. When the leash is attached to the dead ring, the collar does not constrict on the dog’s neck. When the leash is attached to the live ring, the chain slips (adjusts) tighter when pulled and slips looser when tension is released. Training with this leash involves a quick jerk with an immediate release, called a leash pop, snap, or correction. This is supposed to correct a dog’s unwanted behavior, such as leaving the “heel” position. Pulling harder or longer on the choke chain presses on the dog’s esophagus and restricts breathing.