The household registration book is an important material for residents' personal identity proof, and is mainly used in the following aspects: 1. For passport application: Before going abroad, you need to apply for a passport, and the household registration book is one of the necessary materials for applying for a passport. As an identity certificate for international travel, a passport needs to be provided when going abroad for various procedures. 2. For visa application: A visa is a procedure that everyone going abroad needs to apply for, and the household registration book is one of the key materials for applying for a visa. The visa officer will verify the applicant's identity information and family background through the household registration book. 3. For proving kinship: The kinship record on the household registration book can be used to prove the applicant's relationship with other relatives, such as parents, spouse, children, etc. During the process of going abroad, some countries have special requirements for the applicant's kinship, and the household registration book is required as a proof of evidence. 4. For academic certification and degree certification: During the process of studying or working abroad, some countries or schools will require applicants to provide academic and degree certification materials, and the education information on the household registration book can be used as part of it.