Keys, keys and more keys.
Have you ever come across any unknown, unmarked keys such as the ones pictured above?
Did you happen to find them in a strange place where you not only wondered what they were doing in that location, but, more importantly, you wondered what did those keys actually open?
It is hard enough keeping track of which keys open what when you are the owner and you are still alive. Now imagine the problems that arise when you die and someone else is left to figure out the puzzle!