A martingale is a type of dog collar that provides more control over your dog- there is no buckle on it. You slide over your dog’s head when taking on and off. It is made with 2 loops- The larger loop is slipped onto the dogs neck and then the leash is clipped to the smaller loop. When your dog tries to pull the tension of the leash pulls the small loop taut - it pulls the larger loop smaller and tighter on the neck. So they can't escape as easy.