It says on a dictionary that ‘bang’ means to hit violently or noisily. However, I think the following bang means merely put or place because the object is a rat and because Ron ‘placed him’ after the witch’s words.
But why is she saying “bang” in this situation?
(Ron is talking with the consultant witch of a magical pet shop.)
”It’s my rat,” he told the witch. “He’s been a bit off-color ever since I brought him back from Egypt.”
”Bang him on the counter,” said the witch, pulling a pair of heavy black spectacles out of her pocket.
Ron lifted Scabbers out of his inside pocket and placed him next to the cage of his fellow rats, …(Harry Potter 3 [US Version]: p.58)