OPERATING ROOF BOLTER, HOLDING ONTO DRILL STEEL WHILE ATTEMPTING TO COUPLE NEXTEXTENSION. 2ND EXTENSION TOO LONG MOVED DRILL HEAD TO GAIN HEIGHT, CAUGHT THUMB BETWEEN CANOPY & EXDTENSION. CAUS E OF INJURY WAS AWARENESS. COMPLIANCE WITH RULES/REGS WAS NOT A FACTOR. MINING EQUIP WAS A FACTOR, MINER JOB SKILLS WAS A FACTOR, PROTECTIVE ITEMS NOT A FACTOR.