background
barricade
barrier
border
cage
chain
close
cross
danger
door
enclose
enter
entrance
entry
exit
fence
forbidden
freedom
gate
grid
grunge
handle
hard
iron
isolated
jail
keep
key
link
lock
mesh
metal
net
old
open
padlock
prevent
prison
protect
row
rust
safety
security
steel
strong
texture
twisted
wall
wire