Similar to boxing, facking involves at least two people attacking each other with only their feet. Hands must be held behind the back as is custom. Only feet may be used, no other appendage is allowed. Other than this there are no rules, feet may be used in literally any way possible.
Did you see that fack last night? No? Jimmy "clubfoot" Orweeny put his foot through John "the podiatrist" Mahan.
It's Fack (sport)