Preheat a large skillet or griddle on medium heat.
Lightly butter one side of bread slices. Spread non-buttered sides with Thousand Island dressing. On 4 bread slices, layer 1 slice Swiss cheese, 2 slices corned beef, 1/4 cup sauerkraut and second slice of Swiss cheese. Top with remaining bread slices, buttered sides out.
Grill sandwiches until both sides are golden brown, about 15 minutes per side. Serve hot.