Supporting walls

Walls that need this sort of support are clearly ones to walk well clear of. The odd thing was that they looked so solid.

As I've mentioned before, a poem I'm really fond of is the one by Robert Frost 'Mending Wall'. It seems relevant. In it are these lines:

"Before I built a wall I'd ask to know
What I was walling in or walling out,
And to whom I was like to give offence.
Something there is that doesn't love a wall,
That wants it down!"