barrier
blockage
board
branches
care
cleaning
clog
clutter
cork
corrugated
debris
difficulty
dirty
downhill
drain
dry
edge
flooring
flow
furrows
garbage
high
housetop
industrial
leaf
leak
leaked
leaking
leaves
lie
line
litter
metal
modern
obstacle
obstruction
perspective
pollute
profiled
reason
ridge
roof
roofing
sloped
sloping
steel
top
track
trash
way