background
barb
barbed
barbed wire
barbwire
barrier
border
boundary
camp
crime
criminal
danger
dangerous
defense
design
fence
forbidden
freedom
guard
industrial
interdiction
iron
isolated
jail
limit
metal
military
outdoor
pattern
politics
prison
private
prohibition
protection
razor
safety
security
sharp
sky
steel
stop
texture
wall
war
white
wire
zone