Preheat the oven to 450°F and position the oven rack in the middle of the oven.
Assemble the sandwiches:
Lightly butter one side of all slices of bread. Place half of them butter side on the sheet pan and top with sliced cheese. Close the sandwich with the other slices of bread, butter side up.
Bake:
Place the baking sheet in the preheated oven and bake the sandwiches for 6 minutes.
Remove the sheet pan from the oven, flip the sandwiches over, and bake for an additional 2 to 3 minutes, or until the cheese is melted.