Protesters will be allowed to demonstrate in seven areas, but signs cannot be attached to anything that could be used as a weapon. No large backpacks, camera bags, thermos bottles, coolers, picnic baskets, strollers or umbrellas will be allowed on the parade route or the Capitol grounds.
Some people will be watched closely even before getting near a police checkpoint. Metro Transit Police officers have been trained to identify suspicious riders by looking for certain characteristics and patterns, such as people who avoid eye contact or loiter in the stations.
More than 4,600 law enforcement officers will be posted along the parade route. They will include hundreds of undercover officers in the crowd, as well as sharpshooters with rifles on rooftops. An army of Secret Service agents will be inside and on top of buildings along or off Pennsylvania Avenue.
Some of the most critical components of the security plan will be less evident to the public.
John P. Malone, special agent in charge of the Washington field division of the Bureau of Alcohol, Tobacco, Firearms and Explosives, said his agency is bringing in certified bomb technicians and about 20 explosives-detecting dogs from across the country to sweep cars and buildings.
The military will have bomb jammers -- devices that have been used in Iraq and can block or delay someone using a cell phone or other remote gadget from detonating an explosive. Other military assets will be in place, such as engineering companies specializing in rescuing victims of building collapses and forces equipped to deal with a chemical or biological attack.
The anti-terror preparations include the use of mobile and stationary chemical and biological sensors that will sniff the air in subway stations, on the Mall, in buildings and on the streets.
In case of a biological, chemical, radiological or nuclear incident, scientists at Department of Energy laboratories, National Oceanic and Atmospheric Administration meteorologists, Environmental Protection Agency cleanup crews and military and NASA experts will be placed on standby across the country.
Software models developed by the agencies will be tied to the biological and chemical sensors across the city and to wind and radiation monitors downtown, providing detailed alerts and airflow monitoring.
"If we had a release of sarin gas on the Mall, not only will the sensors on the Mall pick it up, we will know the height and density, its direction and how far it has spread," said one federal official. "We did not have this in place before 9/11."
Military radar will monitor the sky from ground stations throughout the city and aircraft aloft.
The Federal Aviation Administration announced that it will triple the no-fly zone over Washington that now prohibits small aircraft within 16 miles of the Washington Monument.
Private flights will be banned from 10 a.m. to 6 p.m. Inauguration Day over the Baltimore-Washington area, defined as the region within 23 miles of Reagan National and Dulles and Baltimore-Washington International airports.
Violators may be intercepted by military fighter jets or customs aircraft and diverted for questioning by agents at regional airports in Easton or Carroll County, Md., or Stafford.