Lightly butter one side of each bread slice. Set 2 of the slices, buttered-side down, on a cutting board. Top those slices each with a slice of the cheese, and then top the cheese with half the sauerkraut. Top the sauerkraut with the corned beef. Top the corned beef with the remaining sauerkraut and then the last slices of the cheese. Top the sandwiches with the remaining 2 bread slices, setting them buttered-side up. Set a non-stick skillet over medium-low heat. Set in the sandwiches and slowly grill 4 to 5 minutes per side, or until the cheese is melted and the sauerkraut and corned beef are heated through. Cut each sandwich in two and serve.