WHEN TRAMMING THE ROOF BOLTING MACHINE ACROSS THE SECTION IT BACAME HUNG UP ON A ROCK ON THE PAVEMENT. THE INJURED GOT OUT OF THE OPERATORS COMPARTMENT AND WAS MOVING THE ROCK OUT FROM UNDER T HE MACHINE WHEN HE FELT A PULLING SENSATION IN HIS LEFT SHOULDER. THE INJURED DID NOT BEGIN MISSING WORK UNTIL 9/17/01.