From Sonic Retro
Fire Knock is Team Rose's variant of the Fire Dunk in Sonic Heroes. When in Power Formation with Big as the leader, Team Rose can enter Fire Combination by pressing , which sees Amy and Cream perch on Big's shoulders as the cat strolls around.
The Fire Knock attack sees the girls spin jump off Big's shoulders, and the cat slugs his teammates baseball-style towards enemies by pressing and hitting them with his fishing rod / umbrella. The attack can also be used to break down doors and other obstacles. When used in the air it is called the Jump Fire Knock.