abstract

background

barb

barbed

barbwire

barrier

border

boundary

captivity

close

closeup

closed

danger

dangerous

defense

detail

fence

forbid

forbidden

freedom

ground

guard

imprisonment

iron

isolated

limit

line

metal

military

no

obstacle

prison

private

prohibit

property

protect

protection

razor

rust

rusty

safety

security

sharp

steel

stop

trespassing

up

war

warning

wire