"Two keys linked together in such a way as to look inseperable. The two keys seem permanently joined. No matter how you look at it, there seems to be no possible way to separate them…or so everyone thinks.
The keys are not inseparable, by any means.
This is just one of those famous puzzles that have enjoyed popularity ever since their creation during the 19th century British puzzle craze.                      The key word is 'Engage'."

-NOB, Cast designer