background

barbed

barbwire

barrier

bird

bleak

border

bound

boundary

chain

cold

crime

criminal

danger

dangerous

doom

escape

fence

forbidden

freedom

grim

guard

guardrail

iron

jail

metal

military

murky

prison

privacy

private

protection

restraint

restriction

safety

secure

security

sharp

sky

spiral

steel

sun

symbol

terror

trees

wall

war

wire