The Reinforced Shield is an item that is only available in Skyward Sword.
The Reinforced Shield is the first upgrade to the iron type of shield. It crafted by taking your Iron Shield to Gondo, the Scrap Shop owner and paying him 50 Rupees along with the necessary items to upgrade it.
The Reinforced Shield adds increased durability, and blocks better than the Iron Shield. It also immune to burning, but it still weak against electrical based attacks. Link can later upgrade the Reinforced Shield into the Fortified Shield.