abstract
background
barb
barbed
barbwire
barrier
black
block
board
border
boundary
building
bundle
cable
danger
design
district
element
fence
frame
ghetto
guard
hank
horizontal
house
iron
isolation
jail
line
metal
object
prison
protective
razor
safety
security
set
shape
sharp
sky
spike
spiral
steel
strong
view
vintage
wire
wired
zone