EMPLOYEE WAS ON 001 SECTION IN #5 RT. HELPING CHANGE THE OPERATOR SIDE OF THE RIPPER JACK. THE BOTTOM OF THE JACK HAD BEEN INSTALLED & THE HOSES ATTACHED. THE JACK WAS CRADLED IN A CHAIN & WHILE ATTEMPTING TO ALIGN THE TOP OF THE JACK IT FELL ONTO HIS RT. RING FINGER; PINNING IT BETWEEN THE JACK & THE PAN.