According to Canadian-born Robin on HIMYM, going to the blue line means just kissing. Otherwise known as first base in American culture.
by Tori L. June 01, 2009
A black rectangle with a solid, thick blue line through the middle. Symbol that is put on items ranging from front license plates, pins, bumper stickers (very small sticker),etc that denotes the user is a police officer. It is a violation of many state's laws to display this symbol if the user is not employed by a police agency. Related to this is the Red Line, which is used to identify fire/medical services personnel. These symbols are usually found on the off-duty vehicles or other personal effects of police /emergency services personnel.
My next-door neighbor, who is a highway patrolman, has a Blue Line tag on the front of his car, as well as a Blue Line sticker.
by J. Malik November 23, 2005