On February 9, 1994, at 2010 central standard time (CST), a Boeing 737-130, N408PE, operated by, Continental Airlines, Incorporated, of Houston, Texas, as Flight 381, and piloted by an airline transport certificated crew, received minor damage during a landing onto Runway 32 Left (13,000' X 200' concrete with patchy snowpack) at the Chicago O'Hare International Airport, Chicago, Illinois. The 14 CFR Part 121 flight was operating on an IFR flight plan. Visual meteorological conditions prevailed at the time of the incident. The flight crew, four flight attendants, and 94 passengers reported no injuries. The flight departed Newark, New Jersey, at 1800 EST. Before departing Newark, New Jersey, the airplane had been involved in maintenance activity. After the maintenance work had been completed, the airplane was removed from the hangar and positioned by the departure gate. Before moving it from the hangar, wheel chocks were removed from the front and rear edges of the tires. A mechanic placed a set of wheel chocks in the left main landing gear wheel well's inside lip edge. The airplane was repositioned at the departure gate. The company's general maintenance manual presented the chocking requirements for all its airplanes. Under the section entitled "Responsibility for Installing and Removing Chocks at Terminal Ramps" the person responsible for removal of the chocks is told: "Chocks are to be stored properly after each use. DO NOT leave lying on open ramps and gate areas." The first officer stated he did the walk-around inspection of the airplane. He said the walk-around was done during night conditions with snow, and blowing snow. The first officer said he was concerned about the snow on the wings. The first officer stated he did not see the wheel chocks in the wheel well when he did the walk-around inspection. He said he used a flashlight with two "D" sized batteries during the inspection. The first officer was asked to describe the walk-around process. His description matched the instructions found in the company's Boeing 737-200 aircraft flight manual (AFM). He was asked to describe the inspection of the main landing gear wheel wells in detail. His description matched the instructions found in the AFM. The AFM does not mention looking for debris in the wheel wells'. According to the AFM, the wheel well inspection is accomplished by: "Check(ing) wheel well area for general condition and hydraulic leaks and main gear viewer clean." The remainder of the inspection describes specific, mechanical, items that require viewing. There was no mention of wheel chock identification and removal. The company mandated a predeparture walk-around for all revenue flights. This inspection is accomplished by a lead safety agent and occurs before pushback from the passenger gate. The company's airport operations manual established the criteria for the agent's walk-around inspection. The only action associated with the airplane's landing gear was ensuring the landing gear down-lock pins had been removed. There was no mention of wheel chock identification and removal. The company's station services training manual entitled "Narrowbody Aircraft Pushback Procedures" does not discuss the placement of wheel chcoks when an airplane is to be moved or parked. A maintenance supervisor from Newark, New Jersey, said the lead agents do not inspect the wheel well's interior. He said the lead agents do not carry flashlights during night inspections. As the airplane approached the airport the first officer asked for the landing gear to be extended. After the landing gear handle was placed into the down position, the pilots observed two green lights and one red light. The red light was the left main landing gear warning light that told the pilots the landing gear was not extended. According to both pilots, they cycled the airplane's landing gear many times with the same gear warning light display upon each extension. The first officer said he went into the airplane's passenger cabin and looked at the landing gear through the landing gear viewing port. He said he was not able to figure out why the landing gear would not extend. Both crew members said they discussed the next decision concerning the flight. They agreed to making a landing with a partially extended left main landing gear. Upon touchdown the captain said he used right engine reverse thrust to maintain directional control. When the airplane stopped, the captain had the passengers deplane out the airplane right forward door. The on-scene investigation revealed that two, black rubber, wheel chocks were wedged between the inboard left main landing gear tire and the wheel well lip. Each chock had a piece of reflective yellow tape affixed to each of its three sides. During the first on-scene wheel well inspection the chocks were not observed using a flashlight having two new "D" sized batteries. A second inspection of the wheel well was conducted using a flashlight having six "D" sized batteries. The chocks were found during the second inspection.