B737-300 EXPERIENCES GEAR UNSAFE CONDITION. RECYCLING OF GEAR CLEARS PROBLEM. SUBSEQUENT INSPECTION DISCOVERS GROUND CHOCK IN GEAR WELL WHICH IMPEDED EXTENSION/RETRACTION MECHANISM.

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UPON GEAR EXTENSION AT ZZZ ARR; L MAIN GEAR UNSAFE INDICATOR LIGHT REMAINED ILLUMINATED WITH NO ILLUMINATION OF ASSOCIATED GREEN GEAR DOWN AND LOCKED INDICATOR LIGHT. A MISSED APCH WAS CONDUCTED AT APPROX 1000 AGL AND AFTER THE QRH 'MANUAL GEAR EXTENSION CHKLIST' WAS ACCOMPLISHED WITH NO CHANGE OF L MAIN GEAR POS INDICATIONS NOTED; AND THE 'GEAR DOWN LOCKED VISUAL INDICATOR' CONFIRMED THE GEAR NOT DOWN/LOCKED; AN EMER WAS DECLARED. #2 VHF UTILIZED ON ZZZ1 OPS FREQ TO CONTACT DISPATCH AND MAINT CTLR. THE FLT ATTENDANTS WERE ADVISED TO PREPARE THE CABIN. MAINT CTL CONCURRED WITH TRYING ONE CYCLE OF THE GEAR HANDLE WHICH RESULTED IN NORMAL GEAR DOWN AND LOCKED INDICATION. THE VISUAL INDICATOR WAS 'RE-SIGHTED' AND CONFIRMED THE DOWN/LOCKED POS. ATC AND FLT ATTENDANTS WERE ADVISED OF THE RESULTANT GEAR STATUS AND A NORMAL LNDG WAS MADE WITH EMER VEHICLES FOLLOWING US TO THE GATE. LNDG FUEL WAS 3500 LBS AND MINIMUM FUEL HAD BEEN DECLARED PRIOR TO FINAL APCH. AT THE GATE A NONSTANDARD CHOCK WAS DISCOVERED WITHIN THE WHEEL WELL BY ZZZ1 MAINT PERSONNEL. THE CAPT (MYSELF) DID THE WALKAROUND AT OUR DEP POINT WITH FLASHLIGHT IN HAND. I UNDERSTAND THAT THE WHEEL WELL AREA IS TO BE CHKED FOR 'GENERAL CONDITION; HYD LEAKS; MAIN GEAR VIEWER CLEAN AND WHEEL WELL LIGHT ON;' IN ADDITION; 'CLOSE INSPECTION TO DETERMINE THE ABSENCE OF FOREIGN OBJECTS' IS ALSO REQUIRED. SUGGESTIONS: I WOULD RE-EMPHASIZE THE NEED FOR FOCUSED CLOSE INSPECTION OF THE WHEEL WELL AREA DURING THE PREFLT EXTERIOR INSPECTION. I MYSELF WILL BE MORE CLOSELY FOCUSED IN SEARCHING FOR FOREIGN OBJECTS DURING THE WHEEL WELL INSPECTION. I WOULD ALSO SUGGEST RE-EMPHASIZED PROHIBITION ON THE PLACING OF OBJECTS IN SUCH AREAS. FINALLY; I WOULD SUGGEST THAT MAINT DO AN EXTERIOR INSPECTION AFTER MAJOR MAINT PROCS WITH AN ASSOCIATED ACFT LOGBOOK ENTRY. THIS NOTATION WOULD ALSO SERVE TO ALERT FLT CREWS OF THE PREVIOUSLY CONDUCTED MAJOR MAINT.