Many people find antique cabinets to be a beautiful and practical addition to their homes. A common problem, however, is that the keys used to open them are lost over time. This makes for a dilemma because even though the cabinet brings charm to your home, its practical uses may be nonexistent. Fortunately, these old cabinets often used skeleton keys. These keys weren't incredibly detailed, leaving the cabinets to be easily opened by other means.
Place the nail file vertically into the keyhole if the keyhole is big enough to allow passage without ruining any of the cabinetry.
Keep the nail file vertical, slowly turning it horizontally until it can't move anymore. Try opening the cabinet. If the nail file is too big, try the clothes hanger method in the next step.
Straighten the curved end of the clothes hanger until it becomes fairly straight. Bend about a quarter of an inch on the end of the hanger with the needle-nose pliers until it creates a 90-degree angle. Insert the end of the hanger and twist like you would with the key.
Use a small Allen wrench if the clothes hanger method doesn't work. Put the curved side of the Allen wrench face down into the keyhole and then turn like you would a normal key.
Check your local hardware store for generic keys if nothing else works. Old skeleton key locks are not secure and can usually be opened by a key with a relatively similar shape.