Mix mayonnaise and chili sauce; spread over each slice bread.
Arrange corned beef, cheese and sauerkraut on 4 slices bread; top with remaining bread slices.
Arrange sandwiches in circle on paper towel-lined 12-inch plate.
Cover with paper towel and microwave on high (100%) 1 minute; rotate plate 1/2 turn.
Microwave until cheese is melted and filling is hot, 1 to 2 minutes longer.