architecture

armed

background

barb

barbed

barricade

barrier

blue

border

bottle

boundary

brick

broken

cement

concrete

covered

danger

dangerous

dark

day

defense

dirty

edge

enclosed

fence

focus

forbidden

fragment

glass

green

guard

old

outdoor

particle

piece

pointy

prevent

private

protect

protection

quality

security

selective

sharp

sky

thief

top

ugly

view

wall

wire