Harry witnessed Professor McGonagall walking right past Peeves who was determinedly loosening a crystal chandelier and could have sworn he heard her tell the poltergeist out of the corner of her mouth, 'It unscrews the other way.'
—Harry Potter and the Order of the Phoenix
Presumably this means that either:
- Peeves is not very good at remembering which direction is clockwise and which is counterclockwise, or
- Hogwarts has a bunch of reverse-threaded screws.
Either of these sound plausible. Is there any further canonical evidence that one or the other is actually true?