entrances are closed, they must give the same degree of protection as the
g. Type field perimeter fence. A combination of concertina fencing
may be used.
This is a double-barbed wire fence with five rolls of
concertina between the fences (cattle fence). (See Figure 2-2.)
Cattle fence of double-barbed and concertina wire
h. Tanglefoot wire.
(1) Barbed wire or tape may be used differently in appropriate cases.
One example is to construct a tanglefoot obstruction either outside a single
perimeter fence or in an area between double fences. This is done to provide
an additional deterrent to intruders.
(2) Hampers ground maintenance.
Security Requirement for Utility Openings.
a. Utility openings include sewers, manholes, and drainage ditches.
Also included are culverts, vents, and ducts.
These provide access to
criminals for sabotage, espionage, and theft. (See Figure 2-3.)
b. Sewers, air and water intakes, and exhausts with openings of 10
inches or more in diameter must be protected with rods and bar grills.