smiles, frowns, and upside downs

smiles, frowns, and upside downs - (informal) The accidental deviations from the uniform alignment of envelopes on a facer-canceler or letter sorting machine. When the back of the envelope faces the machine or operator, it is either a smile (flap makes a V) or a frown (flap is inverted); when the address side faces the machine but is inverted, the envelope is called an upside down.