“What were you doing out of your dormitory at four in the morning?” said Bill, surveying his mother with amazement.
Mrs. Weasley grinned, her eyes twinkling.
“Your father and I had been for a nighttime stroll,” she said. “He got caught by Apollyon Pringle - he was the caretaker in those days - your father's still got the marks.”
I'm not sure what 'marks' refers to. Is it the marks for each house, the marks on his father's body or something else?
From Harry Potter and the Goblet of Fire.