army
arrest
barb
barb wire
barbed
barbed wire
barbwire
barrier
bars
black
border
boundary
camp
crime
danger
defense
fence
forbidden
forces
freedom
guard
illustration
iron
isolation
jail
keep
locked
metal
military
prison
private
private property
property
protect
protection
protective
razor
safety
secure
security
shape
sharp
silhouette
spike
spiked
steel
trespass
war
wire