On June 22, 2006, at 1230 central daylight time, a Cessna R182, N6124T, registered to a private owner, operating as a 14 CFR Part 91 positioning flight, experienced a failure of the main landing gear to extended on landing at Lebanon Municipal Airport, Lebanon, Tennessee. Visual meteorological conditions prevailed and no flight plan was filed. The airplane received substantial damage on landing roll out. The airline transport rated pilot reported no injuries. The flight originated from Jackson, Mississippi, on June 22, 2006, at 0900. The pilot stated upon arrival in the Lebanon area, he tuned up the ATIS information for the airport and began the before landing checklist. He activated the landing gear lever, the nose gear extended; however the main landing gear did not extend. The pilot completed the landing gear malfunction procedures with negative results. The pilot contacted personnel on the ground at Lebanon Municipal Airport over the UNICOM radio frequency. The pilot advised the ground personnel of his problem, entered left traffic for runway 01, and made a low pass down the runway for ground personnel to observe the landing gear. The ground personnel informed the pilot the nose landing gear appeared to be extended, and the main gear was "dangling." The pilot remained in left closed traffic and landed on runway 01. The airplane went off the left side of the runway on landing roll out. The left wing tip and left horizontal stabilizer collided with the ground. The left horizontal stabilizer received structural damage. Examination of the landing gear well by the pilot after exiting the airplane revealed the presence of hydraulic fluid on the airframe. The registered owner of the airplane stated the airplane was flown from Culpeper, Virginia, on March 18, 2005, to Jackson, Mississippi, where it has been based until the day of the accident. The airplane was being repositioned to Lebanon, Tennessee, by the accident pilot. The airplane had been flown three times since its arrival in Jackson, Tennessee. The annual inspection was performed by a local fixed base operator in Jackson, Mississippi, on November 7, 2005. The airplane has not been flown since the annual inspection except for the accident flight. The FAA inspector who responded to the scene stated the airplane was recovered from the accident site to a hanger and the airplane was placed on jacks. The airplane seats and main gear actuator access plate were removed to locate the origin of the hydraulic leak. The hydraulic reservoir was serviced and the hydraulic system was pressurized. Hydraulic fluid was observed exiting the right gear hydraulic down line. Further investigation revealed a longer screw (NAS221-16), designated for a different location, had been reinstalled to secure the inspection panel and penetrated the hydraulic down line. The FAA inspector stated this resulted in a complete loss of hydraulic fluid in the down line and failure of the main landing gear to extend. He stated review of the Cessna R182 and TR182 Parts Catalog, Figure 37, Floorboard Installation, requires a NAS221-12 screw be installed in this location.