The locking option for the Westchester or Oxford mailbox includes of a solid brass insert with lock and two keys. The letter carrier inserts the mail through the incoming mail slot - very difficult if not impossible to get a hand through. You remove the mail using your key - 2 supplied. The locking insert comes pre-installed. The locking insert is attached using the same hardware that affixes the mailbox to the post. It can be added later. For Westchester $79.99. For Oxford $105.49