Sorry for being unclear. In general you can't copy joints and you probably shouldn't even rename them. Many joints can however, share the same value for things like thrust. You can use a slider for instance, so they act in unison. a "$" in front of a variable name makes it global so it can be essentially called from all of your joints. I'll try and make a little video and post it to do a better job of explaining it. Hang in there, once you get past a few quirks sketchy physics combined with a little ruby scripting is loads of fun.