Peace Officers Memorial Day, which honors police officers who lost their lives in the line of duty, is Monday, May 15.
Postal Service facilities are required to fly the U.S. flag at half-staff. When the U.S. flag is flown at half-staff, all other flags must fly at half-staff, too.
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.
The USPS Administrative Support Manual has guidelines on U.S. flag display and maintenance.