Prison Break Minigame

Thought I'd share an unconventional challenge I used in a prison break session recently. The party managed to get out of their cells in the brig of the ship and acquired a ring of keys. The door to the upper decks was at the end of the main corridor. The party had to find the right key from the ring before guards made their rounds.
The staircase is narrow, so only one player could try at a time.