Safety Deposit Box

Safety Deposit Box is an achievement added in the add-on to Fallout: New Vegas, Dead Money.

Walkthrough
To trap Father Elijah in the Sierra Madre's Vault, you must:

1. Talk Elijah into coming down into the vault. 2. Immediately leave the vault and book it through the LEFT entrance of the room. 3. Backtrack all the way to the elevator that you arrived in. 4. Around the time you get anywhere close to the elevator, Elijah will realize that he's been tricked, and set off the alarm. 5. He's stuck in the room. All you have left to do is leave on the elevator. 6. Enjoy your Achievement.