1. Security interest, the symmetry of "usufruct".
 2. It refers to other real rights or restricted real rights.
 3. In order to guarantee the realization of creditor's rights, the debtor or a third party provides a specific thing or right as the subject matter and creates a limited real right.
 4. Such as mortgage, pledge, lien, etc.
 5. The real right for security does not aim at the physical use of the subject matter, but focuses on its exchange value to ensure the performance of the debt, so it is also called "value right", and its subject matter must have exchange value.
 6. As for the change of the value form of the object of right, it does not affect the existence of the security interest.
 7. Therefore, the real right for security has the property of subrogation, that is, when the subject matter of the real right for security is transformed into other forms of value, the real right for security takes the deformed object as its object.
 8. The real right for security is dependent on the existence of creditor's rights.