arrest
background
barb
barbed
barrier
blue
border
boundary
cage
camp
closed
concept
concrete
crime
danger
dark
design
enclose
fence
forbidden
freedom
graphic
guard
imprisonment
industry
inside
iron
jail
lock
mesh
metal
military
nobody
obstacle
prison
protection
razor
security
separation
sharp
silhouette
sky
spiked
spiky
steel
wall