What your testicles or balls would "dock" against when getting oral sex. Chin.
guy 1: I'm going to face fuck that girl so hard my balls will be banging against her ball dock.
guy 2: Excellent!
Chin, the lower part of the face where testicles (balls) would end up if given oral sex by that person.
Scott said, "hey, look at the hairy ball dock on that crack whore!
"Nice ball dock on that new girl, eh?" Scott querried.