How do I merge two items?

[jaustin]

I have a circle that 2.25 diameter and I have a pattern of a dog
I want the circle be around .100 deep and then I want the bog to be about .150 inverted below the bottom of the circle.
When I put the dog on the center of the circle it disappears.

Basically I am trying to create a mold.

I attached it to this post.

dog.mpc

[jaustin]

Think i figured it just click substractive. now it look like it below .100 surface.

[fwharris]

Is this what you are trying to do?

I also inverted the bull dog.

[jaustin]

Yes exactly what I was trying to do.

I found a tip and trick pdf and found where it was talking about subtractive.