As an Army and Navy custom, the flag is lowered daily at the last note of retreat. Special care should be taken that no part of the flag touches the ground. The Flag is then carefully folded into the shape of a tri-cornered hat, emblematic of the hats worn by colonial soldiers during the war for Independence. In the folding, the red and white stripes are finally wrapped into the blue, as the light of day vanishes into the darkness of night.
This custom of special folding is reserved for the United States Flag alone.http://www.usflag.org/