THE TAILGATE WAS SLIGHTLY PROPPED OPEN W/EXCESS MATERIAL. WITH HIS LEFT INDEX FINGER ON LOCK SHAFT, HE STARTED TO PULL THE BOTTOM OF THE TAILGATE OPEN TO ALLOW THE EXCESS TO FLOW OUT. HIS LT T HUMB WAS SLIGHTLY TOO HIGH, & IT GOT PINCHED BETWEEN THE SHAFT & THE LATCH. HIS THUMBNAIL WAS ALMOST COMPLETELY TORN OFF. THIS DID NOT INVOLVE THE MINE SYSTEM OR ANY MINE EQUIPMENT.