What should be the maximum gap between the wires/metal members in case of fence for perimeter security to preclude the possibility of unfettered movement of objects to and from the facility ?

According to the Central Industrial Security Force (CISF) guidelines for industrial and perimeter security (as detailed in the CISF Organization and Functioning Handbook), the maximum gap between the wires or metal members of a fence should not exceed 6 inches. This specific dimension is mandated to preclude the possibility of unfettered movement of objects—meaning the unauthorized passing of items through the fence—and to prevent individuals from squeezing through. Other standard security specifications for sensitive facilities include a minimum fence height of 8 feet and the installation of a 2.5-foot anti-scaling overhang. These physical security standards are designed to deter, delay, and detect unauthorized access to protected installations, ensuring the safety of critical infrastructure and personnel.