background
barb
barbed
barbwire
barrier
border
boundary
camp
crime
danger
dangerous
defense
depression
enclosure
fence
forbidden
freedom
guard
guarded
imprison
iron
isolated
jail
locked
mesh
metal
military
prevention
prison
private
protect
protection
protective
rust
safety
secure
security
sharp
spike
spiral
steel
torture
twisted
violence
war
warning
wire
wired
wrap