“Hold on, Harry, this’ll do it for ’em!”
-- Hagrid as the wall came out of the tail pipe (DH4)
A solid brick wall erupted from the exhaust pipe behind the flying motorcycle during the Battle of the Seven Potters to thwart the Death Eaters following Harry and Hagrid (DH4).
Three Death Eaters avoided the brick wall, but a fourth shattered his broom on it and fell to earth. The wall was separate from the motorbike and as Hagrid sped up they left it behind.