In Australia, teenagers of age 16 - 17 (depending on which state they're in) can obtain their Learner plates (L's) for driving. L plates require the driver to have a fully licensed driver (one without any plates) accompanying them at all times.
After a certain amount of time, (min. 6 months in some states) L platers can obtain their P plates which enables the driver to drive un-accompanied.
However, the act of flippin' platers sees an L plater swapping his plates around (since they are double sided - one side has an L and the other has a P) to make it seem as if they are a P plater. Illegal but otherwise very useful until you get pulled over.
Guy 1: How DID you get here? There is no way you could have walked from one side of town to the other.
Guy 2: Flippin' plates!