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There is a counter-locking pin inside, which can be locked with a single twist. Of course, the train crew can use the key to reverse the outside or lock it, and you can understand it after careful observation and study or consult with the train crew.
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There is a pin or switch, just break it over
There should be a button in the door that can be locked inside. >>>More
No, the doors are made of composite aluminum, or higher. Ordinary building materials are not sold, and no one enters the demand for small quantities. Besides, the price will be very high.
There will be a small suction button on the wall of the toilet that can be flushed when you are done.
It is also the two ends of the carriage, and some carriages do not have it.
If you're a passenger, you can see a metal (plastic) door lock when you go in, just flip the switch clockwise, or if you're a flight attendant, lock it with the toilet key in that compartment.