http://www.secretservice.gov/presidential_inaugural.shtml

Prohibited Items: As a security precaution, the following items will be prohibited from the Inaugural parade route, the White House reviewing stand and the Inaugural balls: firearms, ammunition, explosives, weapons of any kind, aerosols, supports for signs and placards, packages, coolers, thermal or glass containers, backpacks, bags exceeding size restrictions (8"x6"x4"), laser pointers, animals other than helper/guide dogs, structures, folding or collapsible chairs, bicycles and any other items determined to be a potential safety hazard.
With respect to signs and placards, items must be made of cardboard, poster board or cloth and have dimensions no greater than three (3) feet in width, 20 feet in length and one-quarter (1/4) inch in thickness. Surrendered items will not be returned, nor available for pick-up.