"Thumb wipe!" joke

Banta was driving down the street looking for a place to stop so he could go to the bathroom. He stopped at a bar and went inside.
"Bartender! Where is the bathroom, I really need to go?!" he asked.
The bartender pointed him to the bathroom. So Banta went to the bathroom and looked over to the side. There was no toilet paper!
"Oh no!"
He looked over again and saw a sign that said: If out of toilet paper use your thumb and ask the bartender for a "thumb wipe". "Bartender!" he said.
"What can I do for you?" asked the bartender.
"Um.. there was no toilet paper and I need a thumb wipe.
"Oh," said the bartender. "Put your thumb on the bar."
"On the bar?"
The bartender replied, "Yes, on the bar."
So Banta put his thumb on the bar and the bartender pulled out a hammer and slammed it hard on the Banta's thumb.
Banta's instant reaction was to put his thumb in his mouth.