Chesterton frequently uses the fence or wall as a metaphor in his writings.
My favorite and is this one:
“Catholic doctrine and discipline may be walls; but they are the walls of a playground. Christianity is the only frame which has preserved the pleasure of Paganism. We might fancy some children playing on the flat grassy top of some tall island in the sea. So long as there was a wall round the cliff's edge they could fling themselves into every frantic game and make the place the noisiest of nurseries. But the walls were knocked down, leaving the naked peril of the precipice. They did not fall over; but when their friends returned to them they were all huddled in terror in the center of the island; and their song had ceased.”
It is also apropos to my current life lesson which is this:
When building a fence around your chicken coop you are not to build it strong enough to keep the chickens in but strong enough to keep the carnivores out.
Personally I hate it when it takes a pile of bloody feathers to learn something.