Half a croissant, on a plate, with a sign in front of it saying '50c'
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Ratcheting doorknob prank

Spins left. Spins right. How do I open this thing?!?!
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This prank door latch can be opened by turning the knob clockwise, or by turning the knob counterclockwise, *almost* like a regular mechanism.

However, at any given time, *one* of those two operations (clockwise or counterclockwise) will be useless: the knob will spin freely instead of opening the door, and the other operation will work properly.

Every time the door is closed, which operation properly opens the door, and which operation freewheels, will *switch*.

So if walk up to the door, and open it by turning the knob clockwise, then close the door, and attempt to turn it clockwise again, the knob will spin uselessly. If I then turn the knob counterclockwise, I can open the door.

goldbb, Jun 15 2017

Three way door knobs. http://www.thegreen...open-three-ways.php
[2 fries shy of a happy meal, Jun 16 2017]

Two door knobs [pocmloc, Jun 16 2017]

[link]






       [+] Bonus feature: keeps Alzheimer's patients occupied for hours...either inside, trying to get out; or outside, on the lam from Nurse Ratched.
Sgt Teacup, Jun 15 2017
  

       Improvement. Wrong way locks door for 5 minutes.
pashute, Jun 16 2017
  

       Noice. You should be able to cannibalize one of these, [link], to get some frustrating combinations.   

       Fit the door with ten identical knobs. Only one opens the door. The other 9 spin freely. The reset mechanism randomly changes the active knob each time.
pocmloc, Jun 16 2017
  

       Probably not going to sell many of these in high-rises at the moment.
MaxwellBuchanan, Jun 16 2017
  
      
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