In physical security, the term "perimeter" refers to the outer boundary of a property or facility. This includes fences, walls, gates, and other barriers that mark the edge of the secured area. In contexts where yard space and warehousing are used (such as in industrial or urban logistics operations), the perimeter defines the boundary of company-owned property and is critical for physical access control.

“Fence” (A) and “Wall” (B) are types of perimeter barriers.

“Chain link” (D) is a material used in fences, not a boundary in itself.

Perimeter protection is addressed in Domain 2: Application, Design, and Integration of Physical Security Measures.

???? References:

ASIS International, Physical Security Principles (PSP) Study Guide – Domain 2

Protection of Assets (POA) Manual – Chapter: Perimeter Security

ASIS Glossary of Security Terms