Cut off 1/2 inch diagonally from one end of each hot dog, to create a "fingernail."
Cut puff pastry into 1/2 -inch-by-3-inch strips. Wrap each hot dog in a piece of pastry, overlapping edges slightly and leaving both ends visible. Place "fingers" seam side down on a baking sheet. Freeze for 15 minutes, or cover and freeze for up to 1 week.
Preheat oven to 375°F. Bake until pastry is puffed and golden, 20 minutes. Spread ketchup onto each "fingernail" and serve hot.