Building a car behind closed doors ... Source Song Zhuxi's "The Mean or Ask" Volume III: "As the old saying goes, building a car behind closed doors, the same door, the same method." The example shows that you think you are right, but the road outside the door and the car you built are right. (Yan Fu's Theory of Saving the Nation) Comment on Zhu's The Doctrine of the Mean or ask: "The old saying' building a car behind closed doors' means that its laws are the same." It means: although the car is built behind closed doors at home, it can completely fit the rut when it is taken out. This is because there are certain specifications and sizes as standards. So it is called "behind closed doors, go out together". Naming can be the opposite.