I've googled a bunch and come up with nothing.  I believe the Ubuntu menu 
in the upper right is called the system menu.  It lets us lock or 
shutdown, etc.  See the attached screenshot of that menu from my laptop.

My question is about the button at the bottom, second from the left, 
between the settings button and the lock button.  It has a curved arrow 
and a padlock on it.  If I click on it, the menu vanishes, but when I 
return to the menu that button now looks different -- it has the curved 
arrow but no padlock.  If I click again, it goes back to the way it was. 
So it's a toggle switch, probably related to locking somehow, but I 
haven't been able to figure out what it is changing.

Mike
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