It is suprisingly common in some rather extreme underground uk bdsm clubs, many of which reside in Soho, London.
"Brass Knuckling" is a chain of people all performing a Brass Knuckle upon one another.
A double brass knuckle is referred to as "getting brassed"
2.) - "My vagina hurts"
- "Probably because you got brass knuckled last night."
3.) "Her vagina is very wide, I bet she could take my brass knuckle"
4)let your cum drip down your knuckles
5)punch the girl in the face
husband-"oh that...yeah i gave her the brass knuckles last night."