A bloke walks into a nearby bar and after awhile decides to go to the john and sees a black man having a piss. He looks at his tackle and says, "Bugger me, look at the size of that knob, how'd you get a knob that big?"
"Well," says the black man, "I come from Africa and in my tribe it is a custom to tie a rock onto a piece of string and then tie a rock onto your knob, the bigger the knob, the greater your status in the tribe".
"Wow!" the bloke said, and away he goes.
A few weeks later he goes to the same bar, and in the john is the black guy again, "Hi there," he says, "I'm taking your advice and I've tied a brick to my knob to make it bigger".
"Oh" says the black man "Is it working?".
"Well," says the bloke, "It's starting to turn black!"
