MANY cooks, when faced with a leg of lamb, just preheat the oven and get out the mint jelly. But not Rick Harbaugh. When he looks at a leg of lamb, he gets out handsaws and knives.

By the time he's finished with an 8- to 10-pound leg of lamb, it's been cut into four inch-thick sirloin chops (or a small sirloin roast), cubes for stew, strips for stroganoff or wok cooking, tenderloin filets, cubes of sirloin for fondue and shish kebab, and bones for barley broth or soup stock. That makes the basis of seven, count 'em, seven different meals. A week's dinners for two adults and perhaps a child.

This weekend, Harbaugh is demonstrating his divisionary skill at the Howard County Fairgrounds (about 45 minutes north of Washington in West Friendship, Md.), as a part of the 10th Annual Maryland Sheep and Wool Festival. Today's demonstrations are at 11 a.m., 1 p.m. and 2:30 p.m., in the fairground's main exhibit building. A resident of Elliottsburg, Pennsylvania, Harbaugh is a consultant to the American Sheep Producers Council, and travels the country talking about lamb and wool--and offering grilled lamb samples after his meat-cutting demonstrations.

Harbaugh says his method of handling a leg of lamb is economical and easy--especially after he demonstrates how it's done. A handsaw is needed for the initial cut through the bone; after that, using knives, the remaining 3/4 leg of lamb is deboned and butterflied, then divided into four sections following the meat's natural seams.

Harbaugh's demonstrations and samples are just a part of the free Sheep and Wool Festival, which concludes today at 6 p.m. Food stands offer the likes of lamb barbecue and shish kebab, plus vegetarian fare; and the Maryland Sheep Breeders' Association (the festival sponsor) has an education booth where orders can be placed for lamb purchases direct from local farmers.

Food is only part of the focus of the weekend festival; with an equal emphasis on wool, the phrase "food and fiber" is given new meaning. During the day there are spinning, weaving, wool dyeing and working sheep dog demonstrations, a shearing contest, displays of 29 breeds of sheep and handmade items to buy from some 90 craftsmen.

Just in case you can't make it to the festival today, these lamb recipes should whet your appetite for next year's Sheep and Wool Festival. LYNNE CLARY'S LAMB BURGERS (6 servings) 2 pounds ground lamb 1/4 cup plain yogurt 1 teaspoon salt 1/2 teaspoon ground cinnamon 1/4 teaspoon ground cloves 1/4 teaspoon freshly ground black pepper 12 small pita bread pockets Lettuce leaves

Combine lamb, yogurt and spices. Shape into 12 patties. Grill over hot coals for 10 to 15 minutes. Serve with lettuce in pita bread pockets. LEMON LAMBBALL SOUP (3 to 4 servings)

A variation of Greek avgolemono soup. 1/2 pound ground lamb 1/4 cup finely chopped onions 1/2 cup uncooked rice 1/2 cup finely chopped parsley Salt and pepper 2 quarts chicken broth (or a mixture of chicken and lamb broth) 3 eggs Juice from 2 lemons

In a small bowl, combine lamb, onion, rice, parsley and salt and pepper to taste. Make into walnut-sized meatballs. Bring the broth to a boil, reduce the temperature, and carefully add the meatballs. Simmer for 45 minutes to 1 hour. Carefully remove the meatballs with a slotted spoon to a warmed soup tureen. In a large bowl, beat the eggs well and combine with the lemon juice. Very slowly begin adding the broth to the egg mixture, beating constantly, with a wooden spoon or whisk. When all the broth has been beaten in, pour the thickened broth over the meatballs and serve.