The Flag Code, which formalizes and unifies the traditional ways in which we give respect to the flag, also contains specific instructions on how the flag is not to be used.

- The flag should never be dipped to any person or thing. It is flown upside down only as a distress signal.

- The flag should not be used as a drapery, or for covering a speaker's desk or draping a platform. Bunting of blue, white and red stripes is available for these purposes.

- The flag should never be used for advertising purposes. It should not be embroidered, printed or otherwise impressed on such articles as cushions, handkerchiefs, napkins, boxes or anything intended to be discarded after temporary use.

- The flag should not be used as part of a costume or athletic uniform, but a flag patch can be used on the uniform of military personnel, firemen, policemen and members of patriotic organizations.

- The flag should never have placed on it, or attached to it, any mark, insignia, letter, word, number, figure or drawing of any kind.

Source: www.usflag.org