Från LOTR wikia-posten på marken :
Grond was an immense battering ram said to be 60 feet high, 150 feet long, and as thick around as an enormous tree. Fire burned in its great maw. It was operated by a team of great beasts and several trolls were needed to utilize it. The ram contained so much innate evil, that it is said the creatures pulling it would occasionally go mad and run through the battlefield, trampling anything and anyone underfoot. Aided by the "spells of ruin" laid on it during its forging in Mordor, and by the Witch-king of Angmar during the Siege, Grond smashed open the formidable gate of Minas Tirith with just three blows.
Gandalf var rädd för att han visste att grindarna skulle brytas så snart Jord nått dem.