abstract
against
background
barbed
barbed wire
barbwire
barrier
blue
border
boundary
concept
criminal
danger
dangerous
defense
detail
enclosure
fence
forbidden
freedom
guard
iron
jail
metal
military
object
obstacle
old
paling
palisade
pattern
prickly
prison
protect
protection
railing
rusty
safety
security
shape
sharp
sky
steel
symbol
thorn
thorny
wall
war
wire
zone