This Security Hardening Guide serves as a reference for implementing basic security configurations for Merlin series routers. It outlines essential features and operational policies aimed at enhancing security in industrial environments. The guide emphasizes the need for secure installation, compliance with established cybersecurity protocols, and the importance of staff competency in managing and securing networks. It details various security hardening recommendations, including the use of secure boot, VPNs, and firewalls, as well as the implementation of a Public Key Infrastructure. The document also addresses the significance of vulnerability management and the responsibilities of end users in ensuring the correct integration and operation of the routers within their systems. Additionally, it provides guidance on device management, logging, and monitoring practices, which are crucial for maintaining a robust security posture. This guide is intended to assist users in achieving the desired security capabilities before deployment.