One Flew Over The Cuckoo's Nest?

This question refers to the movie, not the book. Near the end, when McMurphy is trying to bust open the window, and one of the black attendants runs over and says something like "Don't want anybody to get hurt now", he wraps a black leather looking things around his knuckles. What exactly is this? Is this some sort of weapon? I'm just curious as to what wrapping a leather strap around your hand does for fighting skills. Best Answer gest ten points. thx