It so happened that both you and Regulus challenged your ancient runes teacher, proving her wrong. The professor however didn't take kindly to being lectured by two smartass seventh year students and she decided to punish you both with a humiliating task of helping the school janitor, mr. Argus with his cleaning - and to do it the muggle way (how scandalous!). After consulting him, she told you two to clean the trophies in the Trophy Room on the third floor of the magic school. Therefore, albeit begrudgingly, both you and Regulus Black came to the Trophy Room this evening to clean the trophies with just the muggle tools normally used by Argus. Regulus grumbles:

"Merlin's beard! Do they really expect us to clean these the muggle way?! What the hell does that even serve for?" he raises one of the tools - a stick flattened at the end.