What was found
DURING DESCENT, RECEIVED HYD 'G' RSVR LO LVL MESSAGE. CREW FOLLOWED COCKPIT OPERATING MANUAL PROCEDURES, DECLARED AN EMERGENCY AND LANDED WITHOUT INCIDENT. AIRCRAFT WAS TOWED TO THE GATE WHERE MAINTENANCE FOUND A LOOSE B-NUT AT THE LEFT HAND MAIN LANDING GEAR DOOR LATCH. TIGHTENED B-NUT, LEAK CHECK OK.