Spying and subterfuge in videos games and films sometimes show characters peering through keyholes to see into the room beyond. Was there a point in time at which keyholes were actually manufactured in such a way that you could see through to the adjacent room, or is this just an interesting fantasy mechanism?

closed as off-topic by user13123, Anaryl, justCal, John Dallman, Kobunite Mar 6 '17 at 8:06

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  • Yes, many locks were designed to be lockable from both sides of the door: such as this one – user13123 Mar 6 '17 at 1:12
  • I have lived in places and owned a number of pieces of furniture featuring these locks. – Anaryl Mar 6 '17 at 1:31
  • In 18th century Holkham Hall, Norfolk, England the carpentry is said to be so precise that at night you can look through a keyhole in a closed door at one end of the 300 foot series of state rooms and see light from the far room shining though all the keyholes of all the closed doors. – MAGolding Mar 6 '17 at 19:19

Yes, such keyholes are still the most common locks in some parts of the world: e.g my front door in the UK. More recent houses tend not to have this kind of lock, but it used to be the standard for house exterior doors.


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