Spread 2 slices of rye bread lightly with mayonnaise or Thousand Island dressing. Put a layer of sauerkraut over one slice, then top with a slice of corned beef then a slice of Swiss cheese. Top with the second slice of rye, mayonnaise side down. Butter outside of reuben sandwich lightly with soft butter or margarine and toast on a griddle or grill, turning to brown evenly.