arc
arch
archway
balance
barricade
barrier
block
bound
boundary
cage
caged in
chain
chain link
city
close
color
confine
curve
curved
danger
defence
defense
developed
dimensional
encircle
enclose
enclosure
fence
fortify
geometric
grid
guard
hard
horizontal
industrial
industrialized
industry
jail
lines
link
links
lock in
mechanical
mesh
metal
metropolitan
net
no entry
obstruction
passageway
path
pattern
perception
perspective
prohibited area
railing
repetition
repetitive
rhythmic
screen
security
semicircle
separate
shape
sidewalk
steel
stockade
stop
strong
sunlight
surround
surrounded
symmetry
texture
tunnel
tunnel fence
urban
urban tunnel
wall
wire