Boolean modifier not cutting out shape properly

This is really strange because I am sure I have been following tutorials properly but obviously not… And sometimes I can get this to work but other times I get weird results.

First I have a big box and have applied the boolean modifier, set it to difference and set the object to my cube just to the right:

Then I move the “cube” object into the area of the large object expecting it to cut that cube object’s area from the large object:

But rather than “subtracting” the cube it sort of appends it… after I click apply this is what I get:

Does anybody know where I have gone wrong? I can’t seem to consistently produce the correct results… Thanks in advance for any replies :slight_smile:

Rough guess, check the normal direction on both objects, when difference and union work in reverse it’ll most likely be something has been turned inside out, go into solid mode is the box black? can also go into edit mode and check face normals to see direction, jump into edit mode and go to the uv tab down the side of tools menu flip or recalc normals. How did you initially make the inside of the main box?

The boolean modifier is finnicky. It might be that you need to do an Alt-A on your objects first.