to before the earliest of the Pharaohs. Today's fashionable dog collars come in a wide variety of designs, patterns and materials and may include accessories, such as bow ties and flowers. Training collars Several types of collars are used for the purposes of training dogs, though sometimes a collar is not used at all (such as in the case of dog agility training, where a collar could get caught on equipment and strangle the dog). Each training collar has its own set of advantages and disadvantages (briefly outlined below) which trainers might consider before using a select one. Training collars are typically used for training only and not left on the dog's neck all the time, as some collars can be harmful or dangerous if left on a dog unsupervised. Flat collars Some dogs are trained on leash using a buckle or quick-release collar. Martingale collar Martingale collars are recommended for sighthounds because their heads are smaller than their necks and they can often slip out of standard collars. They can, however, be used for any breed of dog. Their no-slip feature has made them a safety standard at many kennels and animal shelters. A martingale collar has 2 loops; the smaller loop is the "control loop" that tightens the larger loop when pulled to prevent dogs from slipping out of the collar. A correctly adjusted martingale does not constrict the dog's neck when pulled taut. Others use them fitted snugly to be able to use them in a similar manner to a choke chain but without the unlimited constriction of a choke chain. The structure allows the collar to be loose and comfortable, but tightens if the dog attempts to back out of it. Head halters Head halters, also called head collars, are similar in design to a halter for a horse. They are sold under several brand names. Brands include Comfort Trainer, Canny Collar, Halti, Gentle Leader, and Snoot Loop amongst several others. Brand names are also used when referring to these collars most commonly Halti or Gentle Leader. This device fastens around the back of the neck and over the top of the muzzle, giving more control over a dog's direction and the intensity of pulling on a leash than most collars that fit strictly around the neck. Pressure on this type of collar pulls the dog's nose and consequently their head towards the handler. These type