Grond was a gigantic battering ram used to break the Great Gate of Minas Tirith in the Battle of the Pelennor during the War of the Ring.
Mordor ~ www.thelandofshadow.com
Grond was shaped like a great ravening wolf, who's namesake was Grond, Hammer of the Underworld wielded by Morgoth the first Dark Lord of Middleearth.