The Blue represents the officer and the courage they find deep inside when faced with insurmountable odds. The Black background was designed as a constant reminder of our fallen brother and sister officers. The Line is what police officers protect, the barrier between anarchy and a civilized society, between order and chaos, between respect for decency and lawlessness. Together they symbolize the camaraderie law enforcement officers all share, a brotherhood like none other.
There is a solid black flag with a single blue line in it that is flown during a funeral for a fallen officer. Both can be seen during an officers funeral and flown at the homes of officers and family members of officers.
There is also a similar design for Fire Fighters which replaces the blue line with a red one.