INJURED EE WAS REMOVING GRATING AT A RAIL CAR UNLOADING HOPPER. THE GRATES HAVE LIFTING BRACKETS ATTACHED THAT SLIDE UP TO ALLOW THE FORKS OF A FORKLIFT TO BE INSEERTED FOR LIFTING. THE EE WAS HOLDING THE LIFTING BRACKETS UP TO ALLOW ANOTHER EE TO INSERT FORKLIFT WHEN HIS LEFT THUMB BECAME TRAPPED BETWEEN THE BRACKET AND THE FORK.