Kentucky Black Tip
When you are fucking your sister in the ass and you are about to cum to quickly because you're so turned on, you pull out ( because it's wrong to cum in your sisters ass ) and smack the head of your cock with a sledge hammer leaving it black and blue and numb thus allowing you to finish fucking your sisters tight little ass all night long without cumming !
Billy said to his sister, sorry Angel I'm about to explode , I better give myself a Kentucky Black Tip !