army
arrest
back
backdrop
background
barb
barbed
barbwire
barrier
border
boundary
camp
crime
danger
defense
enclosure
fence
freedom
guard
illustration
iron
isolated
isolation
jail
metal
prison
private
protect
protection
protective
punishment
razor
safety
seamless
security
set
shape
sharp
silhouette
spike
spiral
steel
stockade
system
violence
war
warning
white
wire
wired