Engineering Technician Hayden Clarke sent us a tip for AutoCAD Civil 3D.
"AutoCAD Civil 3D includes a tool called lineworkshrinkwrap. This command is very useful (although it would be more so in AutoCAD); when executed it draws a closed polyline around the outside of selected objects. It's great as a tool for calculating areas, creating boundaries or borders, etc."
Notes from Cadalyst Tip Patrol: This is a great tool, as the tipster states, to quickly create a closed polyline around selected objects. It can get rather tricky at times, however; if your objects are too far away it will form several closed polylines instead of one.