What are the documents required to board a train to Tibet?

There are three primary documents required to board a train to Tibet. The following are documents needed to board a train to Tibet.

Photocopies of Tibet Travel Permit.
We will send you the scan copies of your permit by email. So you will have to print it out. This permit contains two pages, and you will have to make three copies of it. But if you are taking the train from Chongqing to Lhasa, we will have to send you the original Tibet Travel Permit. So we will have to send it to your hotel.
The Passport
You will have to have a passport. Which number you have used to book your train ticket. The ticket officer will check your passport before issuing your ticket at the Train station.
Train Ticket (Paper)
Please collect your train ticket at the Counters. The reservation number we will send is not good to board you on the train. So we will have to present them with your passport and the Train ticket reservation number and collect the train ticket from the counter.

Above are the three documents required to board a train to Tibet. If you are boarding the flight to Tibet, so you will need the original permit in hand.