Barrier

 is a blacklisted block, obtained using glitches and exploits.

Obtaining
Barriers can not be obtained by normal means, however, one popular method includes the use of an Anvil. 1. This results in barrier named "Anvil" appearing in your inventory.
 * Switch to touchscreen controls in your settings.
 * Get an item that can be enchanted with an anvil.
 * Get an enchanted book that has enchantments that can be applied to your item.
 * Drag the anvil inside the UI into your inventory.
 * Once the item gets enchanted, drag it into your inventory as well.

2. This results in barrier named "Anvil" appearing in your inventory.
 * Get a Necron's Blade or its refined versions with 2 scrolls applied.
 * Apply the third scroll onto it.
 * Take the Necron's Blade (or the refined ones) back without closing the anvil menu or shift-clicking.

Description
Barriers are blacklisted. They cannot be stored inside your inventory, backpacks or most containers, and get wiped after about 5-10 seconds. Barriers can be stored with Item Frames or decoration chests.

Uses
When barriers were introduced, they could be placed on your Private Island, however, it was since been patched.