Block

From A Wheel of Time Wiki

Blocks are "barriers" for channelers. They are often found in wilders as a way for them not to know that they are channeling. Blocks make it so a channeler can't channel at will unless certain circumstances are met; some examples are: unless they are angry, if the object is far away, or if someone whom the channeler likes is nearby. A block must be broken to allow the channeler to channel at will.

• Mazrim Taim calls them bars (Lord of Chaos).