abstract
accessibility
background
barb
barbed
barbwire
barrier
black
border
boundary
cage
chain
closed
construction
crime
danger
dividing
enclosed
enclosure
fence
forbidden
frame
grate
guard
iron
isolated
isolation
jail
mesh
nobody
prison
private
protection
protective
safety
security
shape
sharp
silhouette
steel
stockade
system
warning
white
wire
wired