[KenPainter]

The idea is don't tear down the fence until you know why it's there. But a fence across a road - it's so obviously wrong everybody wants to tear it down - not recognizing somebody with a good reason put it there. Big lesson when examining legacy code.

Then there is the Terry Pratchett version, when they move a big piece of furniture to reveal a door with a sign, "under no circumstances should this door ever be opened. " so they open the door and general madcap laughs ensue.