The Scottish Terrier, like most Highland Terriers, was originally bred in order to assist with the work of small game hunters and farmers in Scotland. Virtually everything about the breed was worked for with the singular idea of hunting in mind, and most of those traits still survive to this day, making the Scottie suitable as a working dog despite their rampant popularity as a family pet.
The Scottie has a very good sense for tracking, and has historically proven to be very competitive in contests that are frequently held to see which breed proves the best at this highly valued skill. In addition to their nose, the Scottie seems to possess good eyesight (kept shaded from glaring sunlight by their infamous eyebrows) that allows him or her to sense the motion of even far-away small animals, and their chase instinct causes them to pursue almost immediately. This instinct is so strong that it has in fact become one of the more problematic characteristics for those who simply wish to keep a Scottie as a pet rather than for hunting.
With a solid and powerful body that's nonetheless very compact and low to the ground, the Scottish Terrier can very easily pursue prey such as badgers, hares, and foxes under low-lying brush and into small tunnels where no human hunter could easily reach. Their comparatively large front paws are excellent for digging, and even their short and stocky tail was taken into consideration as it was often used as a reliable means of pulling the Scottie backwards out of a tunnel after he or she had caught the prey in question. Like all terriers, the Scottie also possesses the instinct for dropping and rolling that can allow them to attack the vulnerable underbelly of taller prey; a somewhat sinister interpretation of a playful Scottie's penchant for rolling over to ask for belly rubs.
In addition to his impressive physical attributes, the Scottish Terrier's demeanor is also a valuable resource when they are employed as a working dog. Slow to make friends, but very loyal and territorial once they are won over, the Scottie was a stalwart defender of many Scottish farms, driving away predators and other wild animals that could damage crops or livestock. In this same capacity, the modern Scottie makes for an excellent watchdog.
If you plan to employ a Scottie in a hunting or working role in the modern world, it's important that you take several steps to ensure that this is successful. Firstly, take steps in your training regiment to ensure that you can discipline and bond with your Scottie without repressing the traits that will make them a good hunter, such as digging and their tendency to be mistrustful of strange animals. Secondly, you'll want to ensure their safety by making sure that they're trained to come on command (so you can call them back from any dangerous situations) and that they're up to date on vaccinations and inoculations.