Barrel Shields are items found in Donkey Kong Country 3: Dixie Kong's Double Trouble! and Donkey Kong Land III. These items are, as the name suggests, that blocks enemy attacks. Specifically, Minkey's projectiles. They are found only in the hollow tree levels of the game, first appearing in Barrel Shield Bust-Up in Kremwood Forest. Their appearance is that of a regular Barrel cut in half, with a rope for holding.
As stated above, they are used for blocking projectiles. There are some places, in fact, that the Kongs cannot pass without getting hit with said projectiles, and the Barrel Shield is the only thing that can protect Dixie Kong or Kiddy Kong. The Kongs must get behind the Barrel Shield to be protected, and getting in front will not protect them at all. The majority of Barrel Shields are completely stationary, but a few of them move.