Editing Physical security (section)

=== Physical barriers ===
{{See also|Door security|Window security}}
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|image1 = Security spikes 1.jpg
|caption1 = Spikes atop a barrier wall act as a deterrent to people trying to climb over the wall in [[Aldgate]], [[London]]
|image2 = Border barrier near IBM 9.JPG
|caption2 =  Vehicle barrier at the US Mexico border, 2010
Physical barriers such as [[security fence|security fences]], walls, and [[Hostile vehicle mitigation|vehicle barriers]] act as the outermost layer of security. They serve to prevent, or at least delay, attacks, and also act as a psychological deterrent by defining the perimeter of the facility and making intrusions seem more difficult.
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For example, tall fencing, topped with [[barbed wire]], [[razor wire]] or metal spikes are often emplaced on the perimeter of a property, generally with some type of signage that warns people not to attempt entry. However, in some facilities imposing perimeter walls or fencing will not be possible (e.g. an urban [[office building]] that is directly adjacent to public sidewalks) or it may be aesthetically unacceptable (e.g. surrounding a shopping center with tall fences topped with razor wire); in this case, the outer [[perimeter security|security perimeter]] will be generally defined as the [[wall|walls]], [[window|windows]] and [[door|doors]] of the structure itself.<ref>{{cite book|author1=Talbot, Julian|author2=Jakeman, Miles|name-list-style=amp|title=Security Risk Management Body of Knowledge|publisher=John Wiley & Sons|year=2011|isbn=9781118211267|pages=72–73|url=https://books.google.com/books?id=5xAhp9B1264C&pg=PT73|url-status=live|archive-url=https://web.archive.org/web/20180105015948/https://books.google.com/books?id=5xAhp9B1264C&pg=PT73|archive-date=2018-01-05}}</ref>