Battering rams hung within specially designed sheds.
Siege armies used a battering ram to break down a gatehouse door or even smash a castle wall. To shield themselves from attack, they built a covered shed, in which they hung a thick tree trunk on chains suspended from a beam above. Carpenters tapered the trunk into a blunt point and capped it with iron. The slow forward movement as the battering ram was wheeled toward the castle wall earned it the nickname "tortoise." Soldiers swung the hanging trunk back and forth, and the forward end of the trunk moved in and out of the shed like a tortoise's head, battering its target.
Castle defenders tried to burn the shed down with flaming arrows, though attackers responded by covering the shed with animal pelts or earth to make it fireproof. Defenders sometimes dropped mattresses down to cushion the blows or lowered grappling irons to grasp the trunk, preventing it from swinging.