Preheat oven to 350 degrees.
Toss 12 slices rye bread with 1/2 stick butter.
Layer 2 lbs sauerkraut, 1 lb corned beef, 1 cup Thousand Island dressing, and 1 lb Swiss cheese into a 9 x 13 casserole dish. Press bread on top.
Bake at 350 degrees for 30 minutes.