Let Us Learn How To Grind Rail Joint

New Lessons: 

Let us learn how to grind rail joint ?

What is rail joint? 

Look, it is here :

We railmen are like plastic surgeons,

The pits and rust on the rail,

It's all polished off,

Give it a light!

Don't think it's easy,

It's a delicate job,

It's more than just light

If this joint is not handled properly, it will be like a car wheel driving into a pit,

That bump~

So how can we make the subway not bumpy?

Let me show you ~