Knock, knock.

Oh, no. Wait. It was 'Ding, ding', because Treyen was inside the shop and calling the shopkeeper from that little ringer on the counter (which was meant to be used, correct?).

The third year Hufflepuff was looking for a very old book, and perhaps those people at Flourish had it, but he'd rather check in here first.

And so, he rang the little ringer once more (by accident), and stood very silently, waiting for the shopkeeper.