Spread 1 tablespoon Thousand Island Dressing over each of 6 slices bread. Top with cheese, sauerkraut and corned beef. Top with remaining bread slices.
Spread 1 teaspoon butter over each top slice of bread. Place sandwiches, butter sides down, in skillet. Spread remaining butter over top slices of bread. Cook uncovered over low heat about 10 minutes or until bottoms are golden brown. Turn; cook about 8 minutes longer or until bottoms are golden brown and cheese is melted.