The skilled knuck-giver was the one able to remove the most skin from the recipient’s knuckles! Bloody fun!
single rap from flat face of the cards was 1
single rap from the card edge was 2
Hand sandwich applied with a fist was 10
Food sandwich was 25
A guy I work with described the Flying Knuck as applied by jumping off a park bench and slamming the foot into the hand sandwiched between two halfs of the deck.

I recall my mother wanting this game outlawed.
You knew who lost by the scab that lasted on their hand for a week.
great stuff…especially when the kid picked a red card. He went white!