The term 'Vault Feature' refers to the components of a vault, which is a secure room or chamber used to store valuable items. The three crossword solutions for this term are ARCH (4 letters), GROIN (5 letters), and STEELDOOR (9 letters). An ARCH is a curved structure that forms the top of a doorway or window, while a GROIN is an interior corner formed by two intersecting vaults. A steeldoor is a door made of steel, which is often used to provide extra security for a vault.