Which document helps clarify existing policy requirements in the NISPOM?

The Industrial Security Letter (ISL) serves as an important communication tool in the realm of the National Industrial Security Program (NISP). It is specifically designed to clarify and elaborate on existing policy requirements outlined in the National Industrial Security Program Operating Manual (NISPOM). The ISL provides timely guidance and updates regarding security practices, policies, and procedures that are essential for contractors managing classified information. By disseminating this information, the ISL ensures that all parties involved are aware of the expectations and requirements necessary to maintain security compliance.

In contrast, the other options do not play the same role in clarifying NISPOM requirements. The National Security Policy Directive primarily issues broader national security policies rather than focusing on industrial security specifics. The Facility Security Manual outlines specific security protocols and procedures tailored to an individual facility but does not directly clarify existing NISPOM policies. The Security Compliance Guide serves as a reference tool for compliance requirements but does not specifically address the clarification of existing policy requirements within the NISPOM framework.