Holdout

Holdout Shader.
The Holdout shader node is used to create a “hole” in the image with zero alpha transparency, which is useful for compositing (see Alpha Channel).
Note that the holdout shader can only create alpha when
is enabled. If it is disabled, the holdout shader will be black.Inputs
This node has no inputs.
Properties
This node has no properties.
Outputs
- Holdout
Standard shader output.
Examples

The checkered area is a region with zero alpha.