What defines an "assembly"?

[MSG ANIMOTAKU]

Greetings kerbinauts, I have a question that no doubt someone knows the answer to.

What defines an "assembly" in KSP? I've been trying to duplicate a "Modular Girder Segment" with four "M-1X1 Structural Panels" attached to it, but it won't let me duplicate the whole assembly; I can only duplicate the individual parts. I've tried a few different things to see if I could turn it into one whole assembly and duplicate all of it, but I've not figured out how to yet. So hopefully one or more of you can tell me how, if at all, it's doable.

Edited August 25, 2013 by MSG ANIMOTAKU

[RSwordsman]

You have to alt+click the "root part" or the piece that attaches directly to the rest of the ship. In your case it sounds like the girder. If your segment attaches in more than one place (possible?) then the computer might not be able to determine the part hierarchy for a proper assembly.

[MSG ANIMOTAKU]

I have one girder with four panels attached to each side of it, so the top and bottom are exposed; but whenever I click on the girder, which would be the central object, it doesn't duplicate anything. It just picks-up the girder with the panels attached, as if I had just clicked it. And I know that my alt key works because I can duplicate other things.

[Johnno]

Did you start your craft file with that particular girder? You can't copy your root part. You'd have to place something else first, then the girder, attach things to the girder, then alt-click the girder.

[MSG ANIMOTAKU]

AHA! Thank you good sir or madam. I tried that before but to no avail; I guess I must have done something a little bit different than what you told me. All is good now, and I learned that you can't copy the root part.

I really appreciate the feedback guys. Thanks!