EE WAS CHANGING OUT AN OLD SCREEN CLOTH AND WAS MOVING THE TENSION BAR FROM THE OLD SCREEN. EE WAS GETTING HELP FROM ANOTHER EE. THE FIRST EE WAS PULLING ON THE TENSION BAR TO THE RIGHT WHILE THE 2ND EE HIT THE BAR WITH A LUMP HAMMER DISLODGING IT FROM THE SCREEN FRAME, PINCHING 1ST EE'S LEFT THUMB BETWEEN THE BAR AND THE FRAME.