INJURED PERSON & ANOTHER MECHANIC WERE SLIDING A NEW HYD. CYLINDER INTO THE BOOM TUBE ON LW MULE. WHEN THE HYD. CYLINDER SLID INTO THE INJURED PERSON HE CAUGHT HIS RT. HAND BETWEEN BOOM FRAME & SLATE BAR THAT WAS BEING USED TO HOLD THE CYLINDER. FRACTURE TO FINGER ON RT. HAND.