angle
art
aspect
barrier
boulder
cavity
cell
cement
circle
concrete
creation
draft
fence
gap
globe
gravel
grit
hole
hollow
irregular
jagged
jaggy
lake
marine
mole
ocean
opening
orb
orifice
partition
pebble
peep
peep through
pocket
ragged
ring
rock
rough
roughen
rugged
scoop
scraggly
sea
see
ship
sphere
stone
through
uneven
view point
wall
water