Lockout (sometimes referred to as Emergency Lockout) will immediately 'lockout' the door and prevent access from being granted with a valid card. Access will, however, still be allowed using request-to-exit buttons. Any doors put into lockout and are unlocked via an auto-unlock schedule, or have been unlocked from the Unlock Doors page, will also lock.
To lockout a door, for example, the front entrance door:

