R.T. Rinehart sent in this little-known but useful AutoCAD tip.
Long name, powerful command. Do you ever get polylines that will not join no matter what the fuzz distance is? Perhaps they are all at different z values or whatever? Ever tried to use Bpoly or Bhatch command, with it unable to find a closed boundary, even though everything looks fine? Here is an obscure, but rather powerful, command-line-only command. The command is Lineworkshrinkwrap and I use it to create closed boundaries around selected objects. Just key in the command or write it into a button, select the objects (lines, polylines, arcs, etc.) that you want to shrinkwrap, and this command will create a closed boundary around them — no more pedit headaches.
Notes from Cadalyst tip reviewer R.K. McSwain: To the best of our knowledge, the Lineworkshrinkwrap command is available only in Civil 3D — not in plain vanilla AutoCAD. As R.T. mentions, this command is very powerful and will essentially create a closed boundary out of all selected geometry. If you find it useful, take a few minutes to create a shortcut, type-in command, or a button for your ribbon or toolbars, because typing in that long command name will get old.