Shields the wearer from any light to moderate curses
Shield Hats are magical objects created by Fred and George Weasley and sold at Weasleys' Wizard Wheezes. These hats are enchanted with a Shield Charm (possibly in a manner not unlike how Headless Hats are infused with the Invisibility Spell) and, when worn, shield the wearer from many light to moderate curses, jinxes, and other unfriendly spells. They are useless against the more powerful spells, though, including the Unforgivable Curses. The original purpose was that a witch or wizard would put the Shield Hat on and challenge a friend to jinx them, but the jinxes would not hit the wearer.
Shield Hats were widely used by Ministry of Magic officials and were supplied to them by Weasleys' Wizard Wheezes. The Ministry of Magic officials bought five hundred of them for their support staff in 1996. After this, the Weasley twins began to expand to Shield Gloves and Shield Cloaks as well as all the other items related to Defence Against the Dark Arts. Later items include Decoy Detonators and Peruvian Instant Darkness Powder.
- Harry Potter and the Half-Blood Prince (First appearance)