For each of the hobbits he chose a dagger, long, leaf-shaped, and keen, of marvellous workmanship, damasked with serpent-forms in red and gold. They gleamed as he drew them from their black sheaths, wrought of some strange metal, light and strong, and set with many fiery stones. Whether by some virtue in these sheaths or because of the spell that lay on the mound, the blades seemed untouched by time, unrusted, sharp, glittering in the sun.
'Old knives are long enough as swords for hobbit-people,' he said. 'Sharp blades are good to have, if Shire-folk go walking, east, south, or far away into dark and danger.'
Then he told them that these blades were forged many long years ago by Men of Westernesse: they were foes of the Dark Lord, but they were overcome by the evil king of Carn Dûm in the Land of Angmar.

(LoTR, I-8)

Quickly they searched the bodies of the Orcs, gathering their swords and cloven helms and shields into a heap. 'See!' cried Aragorn. 'Here we find tokens!' He picked out from the pile of grim weapons two knives, leaf-bladed, damasked in gold and red; and searching further he found also the sheaths, black, set with small red gems. 'No orc-tools these!' he said. 'They were borne by the hobbits. Doubtless the Orcs despoiled them, but feared to keep the knives, knowing them for what they are: work of Westernesse, wound about with spells for the bane of Mordor.

(LoTR, III-1)

Out of the wreck rose the Black Rider, tall and threatening, towering above her. With a cry of hatred that stung the very ears like venom he let fall his mace. Her shield was shivered in many pieces, and her arm was broken; she stumbled to her knees. He bent over her like a cloud, and his eyes glittered; he raised his mace to kill.
But suddenly he too stumbled forward with a cry of bitter pain, and his stroke went wide, driving into the ground. Merrys sword had stabbed him from behind, shearing through the black mantle, and passing up beneath the hauberk had pierced the sinew behind his mighty knee.
...
Then he looked for his sword that he had let fall; for even as he struck his blow his arm was numbed, and now he could only use his left hand. And behold! there lay his weapon, but the blade was smoking like a dry branch that has been thrust in a fire; and as he watched it, it writhed and withered and was consumed.
So passed the sword of the Barrow-downs, work of Westernesse. But glad would he have been to know its fate who wrought it slowly long ago in the North-kingdom when the Dúnedain were young, and chief among their foes was the dread realm of Angmar and its sorcerer king. No other blade, not though mightier hands had wielded it, would have dealt that foe a wound so bitter, cleaving the undead flesh, breaking the spell that knit his unseen sinews to his will.

(LoTR, V-6)