Lay the slices of rye bread flat on a cutting board.
Spread Thousand Island dressing evenly on one side of each slice of bread.
On two slices, layer Swiss cheese, then corned beef, then sauerkraut, and top with another slice of Swiss cheese. Place the remaining two slices of bread on top, dressing-side down, to form sandwiches.
Lightly press the sandwiches together.
Spread softened butter on the outsides of both sandwiches, on the top slice only for now.
Heat a skillet or griddle over medium heat.
Place the sandwiches butter-side down into the skillet. While they cook, spread butter on the top slices.
Cook for 3 to 4 minutes per side, pressing gently with a spatula, until the bread is golden brown and crisp and the cheese is melted.
Transfer to a cutting board, slice in half, and serve warm.