To function as a working terrier, he must possess certain characteristics: a ready attitude, alert and confident; balance in height and length; medium in size and bone, suggesting strength and endurance. Important to breed type is a natural appearance: harsh, weatherproof coat with a compact construction and clean silhouette. The coat is broken or smooth. He has a small, flexible chest to enable him to pursue his quarry underground and sufficient length of leg to follow the hounds.