anchor
arrest
attached
background
barrier
big
block
boat
bolt
boundary
brown
chain
chained
chrome
community
connection
cooperation
copy space
dock
exit
fear
fence
hanging
iron
link
lock
locked
metal
metallic
nautical
network
old
opening
portal
prison
rust
safety
security
shiny
ship
solidarity
stainless
steel
strength
strong
team
technology
transportation
white