"Dudley Henriques" wrote
A lot of the guys have a padlock setup on their canopies or doors in the
case of multi-engine stuff. Some aircraft canopy design allows for a hole in
the canopy track you can padlock.

Well... this ain't exactly an example of a "discreet" place to put a
padlock, but anyway... :-)

http://www.aviacaomilitar.com.br/webkits/padlock.jpg

That's P-47D-40-RA n° 45-49151, preserved at the Museu Aeroespacial,
Rio de Janeiro, here in Brazil. And yes, that's me in the cockpit...

Vicente