Correct fore- and hindquarters are essential to correct Scottish Terrier breed type. The forequarters make up the Scottie's digging apparatus while the hindquarters provide the real propelling force of the dog. Also, if a short-legged dog is going to be able to work a long day, every day, and in rough terrain, he must move as efficiently as possible. Good fronts are particularly hard to breed because the forequarters comprise so many different elements: layback, angulation, length of scapula and upper arm,  width and depth of chest, forelegs, pasterns, and feet.

Layback

Layback is the word used to describe the placement of the shoulder blade or scapula. It is normally described by the angle formed by a vertical line drawn through the point of shoulder and a second line drawn from the point of shoulder up the ridge of the scapula  to the tip of the scapula.

Correct layback for a Scottish Terrier is an angle of about 45 degrees back from the vertical. Radiographs have shown that the actual angle is less than 45 degrees but it looks like 45 degrees externally.

Ratio of bone length

Although the upper arm is slightly shorter than the scapula, it appears nearly equal in length when examining the dog. This illusion is caused by the fact that the point of the elbow is included in the visual measurement of the length of the upper arm.

A long upper arm is required so that the front leg is set down well behind the dog's forechest. (See illustration of Chest.)

If the upper arm is too short, the front legs will be too far forward. (Fox Terrier front)