Skeleton Keys

A skeleton Key is a key that was very popular before the 2nd World War. Today it is in use mostly by people interested in Antiques.
"Skeleton Key" is often used by people who refer to a Master Key- a special kety that opens several doors

Master keys can be made in locksmith shops.
Nevertheless, there are Skeleton keys that are long keys with a round hole in the end.
For those keys there is a special brass locks that are antique styled but supply better safety then the traditional Skeleton keys and the fitting locks.