A contraceptive method dating back to the Vikings.
When having sex with a wench who is unsuitable to bear his children, the Viking pulls out and ejaculates on his knuckles then proceeds to punch the wench in the face.
Mike: so what happened with that chick you took home?
Mark: oh not much...we had sex for a while, but i was too lazy to put a condom on, so I ended up just giving her the old viking hammer...
Mike: Pow! Right in the kisser!