The Glasgow Smile (also known as the Chelsea Smile or the Glasgow Grin) is a particularly brutal form of mutilation and torture believed to have originated in the streets of Glasgow during the era of the blade gangs, who would slash victims across the cheeks to give them a horrific "smile" due to scars.
The Chelsea Smile is a similar torture devised by football hooligans in which a victim's cheeks are sliced open, some exceptionally sadistic thugs were said to only inflict a small cut on either side of their victims mouth and put salt in the wound, causing the victim to scream and stretch the wound into a "smile".