Preheat a grill to medium-high. Arrange 3 thin slices sandwich bread, such as Pepperidge Farm Very Thin white bread, on a work surface. Top each with 1 deli-style slice cheddar cheese, another slice bread, another slice cheese and another slice bread. Trim and discard the crusts. Brush the sides of each stack with melted butter. Quarter each diagonally to form 12 triangles. Spear a 6-inch skewer into each quarter and butter the cut sides. Grill each side.