What is this effect called and how do I apply it and unapply it?

[Bmmoffattb]

What's this? I know it allows me to draw over the object (even from layers that are under it) but I don't know what it's called, how to apply it, or how to get rid of it. Some help on finding out what this is and how it works would be nice

[Omar.Fathy]

It is the Layer Knockout.
You can make it from the layer style window in the Blending Options section.
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[Bmmoffattb]

But that doesn't explain this. I don't have that on, but it's still doing it. Also, if I draw under the layer, it still draws under it.

[Chuck Uebele · Accepted solution]

If you select any of the blending options in the layer style UI, you will get that icon. It looks like your blend if slider for the black side is slightly moved: you have it set at 4 for "This Layer" and 9 for "Underlying Layer."

[Bmmoffattb]

Thanks! I found out it was because I tweaked the "underlying layer" setting. Interesting. I think it allows you to draw over the upper layers with lower layers as long as you're using black.

[Chuck Uebele]

Yes, with black, and those settings, it will drop out the image in the top layer, so It looks like you're drawing over it.