This standard specifies the requirements of the locking system for burglar-resistant security doors from resistance class 3, indicated in the UNE-EN 1627 standard. The standard applies to the whole of the door, including its frame, its hardware (pivoting elements, and closing and locking system), and includes recommendations for its installation and maintenance. The standard establishes a classification of the security doors according to additional parameters to the resistance to burglary: the protection against attacks of skill without force on things or with the use of instruments that allow the door to be opened without leaving evidence of the attack, visible to the naked eye, i.e. non-violent attacks and the corresponding documentary control. The standard also defines additional test methods in which the use of new tools is considered for the manual attack and documentary verification, which improve the protection of the locking device against non-violent attacks. These additional parameters define different levels of protection. The standard contains recommendations on possible adaptations or pre-installations to incorporate sensors or detectors, which can be connected to electronic burglar and intruder alarm systems, access control, locking and opening, and their proper installation, as well as the maintenance of security doors.