Thangail, also known as Shield-fence, was a shield-wall formation invented by the Númenóreans and mostly used by the Dúnedain of Middle-earth. It was used as a defense technique to hold-off an attacking enemy. The soldiers would form two closely-packed ranks that would act as shield-walls. These ranks of soldiers would be bent back adjusting for the enemy’s charges keeping either end from being outflanked, and then becoming a closed ring of unbroken shields that would continue fending off further attacks.