On September 30, 2007, about 1505 mountain daylight time, a Bellanca 7GCBC, N41695, experienced the breakage and separation of its left main landing gear during landing rollout at the Laurel Municipal Airport, Laurel, Montana. The airplane was owned and operated by the private pilot, who was receiving flight instruction from his airline transport certificated flight instructor (CFI). The airplane was substantially damaged. Neither pilot was injured. Visual meteorological conditions prevailed at the time, and no flight plan had been filed. The flight was performed under the provisions of 14 CFR Part 91, and it originated from Billings, Montana, about 1400. The CFI reported to the National Transportation Safety Board investigator that he was providing transition flight training to the student, and they had performed a series of uneventful takeoffs and landings. During the accident landing down the center of runway 22, the left main gear separated at the point where a step had been attached, and as the airplane rolled to a stop, the left wing's lift strut buckled. The Federal Aviation Administration (FAA) coordinator reported that his examination of the airframe revealed evidence that the step had been spot welded onto the spring steel gear assembly. The assembly fatigued and broke in the vicinity of the spot weld. The FAA coordinator stated that evidence of corrosion was observed in the area where the gear assembly fractured. No evidence of gear maintenance, including the welding of the step to the gear assembly, was documented in the airplane's maintenance records.