Hi all.

So now I'm getting into the trimming the surface.

I'm trying to remove the top and bottom surface.  So I created an extruded surface and will use that to remove the part that I wanted.

I selected the part that I want to trim.

Well, the part that I want to remove got removed except for the top and bottom surface.

As you can see, the surface removed and added to the inside part per red arrow, but the top surface is still intact.

I tried to edit the sketch and will try to remove it again.

This is the way it should look like once the surfaces are trimmed.

But nope.  Still the same.

I'm sure it's something silly that I missed but for the life of me, I couldn't figure out what I did wrong to remove the selected surface.  Please advise?