flag down

fly the flag

To support one's country enthusiastically.

freak flag

Unconventional or unrestrained behavior; extreme, nonconformist views; the side of one's personality which harbors a tendency toward such behavior or such views.

Hoover flag

An empty (penniless) pocket, turned inside out, showing that someone has no money (especially during the Great Depression.)

raise the flag and see who salutes

To float an idea, (or otherwise do some action) to see what response or controversy (if any) it generates, usually as a preliminary step.

rally round the flag

To unite in order to support one's country, especially during a crisis or war.

red flag

Something that will enrage a particular person; a red rag.

show the flag

Of a naval vessel or military force, to identify itself by displaying the flag of its country of origin, especially in order to establish an authoritative presence and to exert diplomatic or political influence.

strike one's flag

To yield, give up, or surrender.