If you need to turn off the water to unhook a dodgy appliance -- if you're one of those people who says "calling a professional is for suckers" -- remember it's all the way to the RIGHT to turn it off. Not left.
If you turn it all the way to the left, you will wind up drenched from head to toe, shrieking "shit!" and "fuck!" in a not-at-all-impressive falsetto, as your neighbor from downstairs bangs on the door, wondering with justifiable agitation why there's water dripping from his ceiling.
Hope this is useful.