This document discusses physical security and protecting important assets. It outlines the need for physical security to deal with threats like vandalism, theft, and attacks. Physical security should use a layered defense model with layers implemented at the perimeter and moving towards assets to provide deterrence, delay, detection, assessment, and response. When planning physical security, careful facility selection and design can guide access, maximize visibility, and reinforce ownership through natural access control, natural surveillance, and territorial reinforcement. The methodology discussed uses a defense in depth approach with control of access flows. Threats to physical security are also addressed, and the document concludes with a demonstration of effective physical security.