Preheat oven to 425 degree F. Stir together mayonnaise and mustard. Spread on cut surface of bread. Top with cheese triangles. Place in a 15x10x1-inch baking pan.
In a medium mixing bowl toss together meat and sauerkraut.
Divide meat mixture evenly between bread halves in baking pan. Bake, uncovered, in the 425 degree F oven for 5 to 10 minutes or until warm and cheese begins to melt. Serve the sandwiches open face. Make 4 to 6 servings.