Final answer:
The correct 4-letter word for both an iron fitting on a horse's hoof and a card-dealing box in a casino is 'shoe'. It serves as protection for horse hooves and a card holder in games.
Step-by-step explanation:
The 4-letter word that can be used to describe both the iron fitting on the hoof of a horse and a card-dealing box in a casino is a shoe. In the context of a horse, the shoe is a protective fitting made of metal that is attached to the hooves of horses to prevent wear. In a casino, the shoe is a device that holds multiple decks of cards, making it easier for the dealer to deal the cards during a game.