The Border Terrier breed of dog is medium-sized, with a wiry coat that may be red, grizzle and tan, blue and tan, or wheat, always with a dark muzzle. He is good tempered and affectionate in the home. He learns quickly and responds well to obedience training, but must be kept engaged and well-exercised, as he’s an active dog. The Border Terrier breed of dog suggests endurance and agility, despite being rather narrow in shoulder, body and quarter. The body is covered with close-fitting and intensely wiry jacket. The characteristic "otter" head with its keen eye, combined with an "at the alert" body, conveys fearlessness and determination. For his work of running his quarry to earth, he must be alert, active and agile, and capable of squeezing through narrow apertures and rapidly traversing any kind of terrain. The head of the Border Terrier is similar to that of an otter. Eyes are dark hazel and full of fire and intelligence. Moderate in size, neither prominent nor small and beady. Ears are small, V-shaped and of moderate thickness, dark preferred. They are set somewhat on the side, and dropping forward close to the cheeks. They should not break above the level of the skull. Moderately broad and flat in skull with plenty of width between the eyes and between the ears. A slight, moderately broad curve at the stop rather than a pronounced indentation. Cheeks slightly full. Muzzle is short; a dark muzzle is characteristic and desirable. A few short whiskers are natural to the breed. Nose black, and of a good size. Teeth strong, with a scissors bite, large in proportion to size of dog. The neck of the Border Terrier breed of dog is clean, muscular and only long enough to give a well-balanced appearance. Back is strong but laterally supple. Loins are likewise strong. Body deep, fairly narrow and of sufficient length to avoid any suggestions of lack of range and agility. The body should be capable of being spanned by a man's hands behind the shoulders. Brisket not excessively deep or narrow. Deep ribs carried well back and not oversprung in view of the desired depth and narrowness of the body. The underline fairly straight. Tail is moderately short, thick at the base, then tapering. It is carried high when at the alert, but not over the back. When at ease, a Border Terrier may drop his stern. The Border Terrier's shoulders are well laid back and of good length, the blades converging to the withers gradually from a brisket not excessively deep or narrow. Forelegs are straight and not too heavy in bone. Feet are small and compact. Toes should point forward and be moderately arched with thick pads. The hindquarters are muscular, with thighs long and nicely molded. Stifles well bent and hocks well let down. The coat of the Border Terrier breed of dog consists of a short and dense undercoat covered with a very wiry and somewhat broken topcoat which should lie closely and without any tendency to curl or wave. A Border Terrier should be able to be exhibited almost in his natural state, with a simple tidying up of the head, neck and feet. Border Terriers come in red, grizzle and tan, blue and tan, or wheaten. A small amount of white may be allowed on the chest, but white on the feet is penalized. A dark muzzle is characteristic and desirable. The gait of the Border Terrier is straight and rhythmical, free and agile, with good length of stride and flexing of stifle and hock.