If placed on your dog incorrectly, the links of the collar go from the leash through the other ring and then UNDER the dog's neck. If placed on your dog incorrectly, the collar will often not automatically loosen when you pull on the leash.
It is best to receive training from a dog handler or trainer on the proper use of a choke collar. Injuries to dogs have occurred when the collars were incorrectly placed on the dog or used improperly. If your dog is very small or has a respiratory problem, choke chains are not recommended.
If your puppy or dog continues to pull on the leash even while wearing a choke collar, you may want to consider using a halter-type collar.