President Obama has ordered flags flown at half-staff to honor the service members killed in the recent shooting in Chattanooga, TN.
Flags should be flown at half-staff until Saturday, July 25, at sunset.
To fly the flag at half-staff (blue.usps.gov intranet), 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.
Managers at postal facilities that are closed Saturday should leave their flags at half-staff or take them down when they close the previous day.
Source: Flag notice | USPS News Link