Memorial Day is the only day in which flags are flown at half-staff for only part of the day — to both honor the sacrifices of those who gave their lives and to inspire those who continue in their stead.
Photo credit: www.flaginsider.com
On Memorial Day the flag is raised briskly to the top of the staff and then solemnly lowered to the half-staff position, where it remains only until noon. It is then raised to full-staff for the remainder of the day.
The half-staff position remembers the more than one million men and women who gave their lives in service of their country. At noon their memory is raised by the living, who resolve not to let their sacrifice be in vain, but to rise up in their stead and continue the fight for liberty and justice for all. Source: Wikipedia