Martingale collars are a great tool to use on walks. The main difference between a martingale collar and a regular collar is that it tightens up as your dog pulls. The purpose of this is not to choke your dog, but to prevent them from escaping their collar. Many dogs have heads that are the same size or smaller than their neck. With a regular collar, when a dog backs up or wiggles from excitement, they may be able to slip out of the collar. With a martingale collar, when this happens, the collar tightens and prevents it from coming up over a dog's head. Many rescues use this type of collar when training a new dog to walk on leash.