Vault Keys are obtained by interacting with Vaults, which spawns the Vault Keys in the sockets around the circuitry.
Uses
Vault Keys are used to complete the puzzle of a Vault. Rotating and setting in the correct slot will turn them yellow and make a sound to let the player know it is correct. Once the puzzle is complete, the Vault Keys are locked in to the Vault and the Rootkit tray will open.