army
background
barb
barbed
barbwire
barrier
black
border
boundary
chain
closed
construction
crime
danger
dangerous
design
farm
fence
freedom
guard
iron
isolated
isolation
jail
keep
law
metal
military
prevent
prison
prisoner
private
protection
razor
safety
secure
security
shape
sharp
sign
silhouette
steel
symbol
system
war
warning
white
wire