EMPLOYEE HAD EXTENDED THE EXTENSION LADDER IN ORDER TO MAKE REPAIRS TO OVERHEAD ELECTRICAL LINESTHE SLIDES ON THE LADDER BECAME STUCK & HE BEGANSHAKING THE LADDER TO FREE THE EXTENSION. THE EX TENSION SLIPPED FREE & JAMMED HIS LEFT THUMB AGAINST THE LADDER RUNG. MEDICAL ATTENTION WAS SOUGHT & SUTURES WERE REQUIRED TO CLOSE LACERATION TO HIS THUMB.