ASSISTING OTHER ROOF BOLT CREW- HAD HIS LT. HAND LAYING ON THE STATIONARY PART OF THE ROOF BOLTER. WHEN THE OPERATOR HIT THE EXTENTION HANDLE TO SLIDE THE HEAD BACK IN, IT MASHED HIS LEFT RING FINGER BETWEEN THE TRAY & BODY OF THE BOLTER. BROKEN FINGER AND TORN LIGAMENTS ON THAT FINGER.