I don't know where I learned this, but when I'm mailing personal or confidential information, I initial the envelope flap so that if it were to be opened and tampered with, it would be more difficult to properly reseal the envelope because the pen marks have to line up.
Oh crap, and I just realized that I addressed this envelope wrong, too. Dammit.
Oh crap, and I just realized that I addressed this envelope wrong, too. Dammit.