The landing gear on the Mooney M20 are made of heat-treated chrome-molybdenum steel. The main landing gear is attached to the main wing spar, while the nose gear is mounted to the tubular steel frame. Stacks of rubber shock discs act as shock absorbers. All models, with the exception of the M20D Master, came with retractable landing gear; on these models, the nose wheel retracts rearwards and the main wheels retract inwards. Early models use a hand-operated lever system to raise and lower the gear. The manually actuated landing gear are raised by unlocking the lever from just below the throttle, which is called a "Johnson Bar" and is named after the Johnson Bar (locomotive), rotating it to the floor, and locking it into a fixture on the floor. Lowering the landing gear require the same operations in opposite order. Interestingly, the Al Mooney got his start working as young man for the railroad industry, hence the borrowing of a steam locomotive term for use in describing part of an aircraft. Starting in 1969, electrically operated landing gear became standard.