Final answer:
The most common type of perimeter security mechanism is fences, due to their physical presence as a deterrent and barrier. Other significant elements include security guards, CCTV, and lighting, which combined with fencing create an integrated security system.
Step-by-step explanation:
The most common form of perimeter security devices or mechanisms is fences. Fences serve as a physical barrier to both deter and delay unauthorized access to a property. They are visible and can be constructed to various specifications depending on the level of security required, which may include barriers that are difficult to climb, cut, or break through.
Security guards, CCTV, and lighting are also significant elements of perimeter security. Security guards provide a human element of surveillance and response, while CCTV is a vital tool for monitoring activities around the perimeter, and lighting helps to deter intruders and assists in the visibility for both guards and cameras.
In summary, while fences are the most common first line of defense, effective perimeter security often involves a combination of these devices and mechanisms, layered to create an integrated security system.