What is rear door OS?
The OS of a car is the offside. (often written as o/s)Explanation: The side of the car nearest the kerb or pedestrian way when driving on the correct side of the road, is the nearside, or the n/s.The side of the car that is away from the kerb is the off side, or offside (o/s)The rear OS door is the side door behind the driver's door, which is itself the front OS door, or the front door OS.