Shadow control

[DavidacrossAmerica]

I thought that knockout was what you used to control shadows in this situation, but it's not doing what I want it to. There is a red box, and on the top of it is an image with a shadow applied. As you see, the image shadow extends beyond the box. I want it to stop at the edge of the box. How do I do that? 

[Creamer Training]

Are you referring to an inner shadow effect (just below the drop shadow effect)?

[DavidacrossAmerica]

No, this is a "regular," I guess, outer shadow.

[Lukas Engqvist · Accepted solution]

You can mask the object by placing the object inside the red box (paste into and adding the shadow this way limiting to the red box). If there are other elements that make a larger picture you could paste all those objects into an empty frame, where the frabe will work as a clipping mask for applied effects.

Knockout is not for this kind of situations, there is nothing for the shadow to knock out, it is the shadow you want to remove?

[DavidacrossAmerica]

Placing it inside the box did the trick. Thanks.