barb
barbed
barbwire
barrier
block
border
boundary
closed
crime
criminal
danger
dangerous
day
defense
division
fence
forbidden
freedom
frontier
grid
hong
human
industrial
kong
liberty
limit
mai
metal
military
po
prevent
prison
private
prohibition
protection
restriction
rights
safety
security
sharp
sky
spikes
spiral
state
trespassing
violence
wall
wire
zone