How about a visa?

A visa is a note or label affixed by the sovereign organ of a country to the passport or other travel documents held by its own citizens or foreign citizens, and there is a clear explanation on the seal or label to indicate the procedures for allowing them to enter, exit or transit. It can also be said that it is an endorsement certificate issued to them.

Visa is an act of national sovereignty, a concrete manifestation of a country's control and management of citizens of other countries when entering the country, in order to achieve the purpose of safeguarding national security and domestic social order.

Visa and passport:

Passport is the holder's nationality and identity certificate, and visa is the permission certificate of a sovereign country to allow foreign citizens or their own citizens to enter, exit or transit.

Visas are generally endorsed on passports, some are endorsed on other travel documents instead of passports, and some are issued separately. For example, immigration visas in the United States and Canada are A4 paper, and Singapore also issues separate paper visas to foreigners. Generally speaking, a visa must be used at the same time as a passport to be valid.