knock against someone or something
to bump against someone or something. Mickey knocked against Mary and said he was sorry. I didn't mean to knock against your sore knee.
knock something against something
to strike something against something. He knocked a chair against the table and tipped both pieces of furniture over. A chair was knocked against the table, upsetting a vase.
knock (up) against someone or something
to bump against someone or something. The loose shutter knocked up against the side of the house. The large branch knocked against the garage in the storm.