I occasionally see these water bottles positioned on the sidewalk, flush to the wall, in front of Maltese houses:
They have a particular purpose. I didn’t know what it was, and neither did any of our guests. I’m not sure how widespread the practice is, but it wasn’t what I expected.
Can you guess? Locals, keep your mouths shut.
UPDATE: Eoghan and others are correct–they’re apparently a defensive mechanism against wayward dogs. The Maltese folks who explained this to me weren’t sure how effective they were, but it’s interesting that it’s also a tactic used in Ireland and Japan.