Workers were building a union hall. The violists asked why they were digging while the trumpeter supervised. 'Because I'm smarter.' The violist didn't understand. The trumpeter put his hand in front of a tree. 'Hit my hand!' At the last instant he moved it. The violist went back to the ditch. 'Let me explain,' he said to his friend, putting his hand in front of his own face. 'Hit my hand with your shovel!'