831 - The frequency of patrol coverage of outside yard areas, including parking lots, will vary with the facility, exposure to adjacent properties, and storage within yard areas. Perimeter security is a critical element of a site's security and should be an integral part of a site's security program. All entrances to Company property must be protected either with a uniformed guard or an electronic access system. Standard six-foot chain link fencing (mesh no longer than two inches square) with three strand barbed wire angled inward at 45 degrees o top should enclose yard areas adjacent to manufacturing sections of the plant. Sites complying with the European Security Framework must utilize the approved metail fencing described therein. Elsewhere, fencing should comply with local standards and practices. It is not desirable to erect fencing across the Administration Section of a facility which borders on frequently used public roads. Outlying vacant land areas should be enclosed with farm-type fencing with steel posts and including No Trespassing signs at appropriate intervals. Farm-type fencing may be used also on the perimeter of vacant land, if the land is used by railroad tracks serving the facility.