Patriot Day is also known as the National Day of Service and Remembrance.
To fly the flag at half-staff, hoist the flag to the peak for an instant and then lower it to the half-staff position. The flag should be raised to the peak again before it’s lowered for the day.
Facilities that fly the flag at all times and are closed Sunday should lower the flag to half-staff when the facility closes prior to Patriot Day. Return the flag to full staff when the facility opens Monday, Sept. 12.
The Postal Service’s guidelines on U.S. flag display and maintenance have additional information.