INJURED CLAIMS HE WAS SEEMBLING THE RIGHT REAR LEVELING JACK INTO THE HOUSING ON THE 4540 DRILL. THE RAM AND CAP WERE PINNED TOGETHER AND SUSPENDED FROM THE MOBIL CRANE. THE COMBINED WEIGHT IS APPROX 1800 LBS. INJURED WAS STANDING ON A STOOL AND GUIDING THE JACK INTO THE HOUSING. HIS PARTNER WAS BELOW CHECKING THE ALIGNMENT FOR LOWER PIN. INJURED SIGNALLED CRANE TO LOWER JACK AND W