H.H., sorry I screwed up and did not describe what I was trying to do clearly. I would like to take a shape like a square made out of 3d polylines and change it to a solid. First I must close the 3d polylines somehow and then extrude them but I cannot figure out how.
Thanks HH and everyone.
Turn on "Workplane by entity" in the Workplane toolbar or in Workspace|Workplane and click one of the existing 3D polylines. Then select all of them and go to Format|Place on Workplane. Select one of the polylines using the Edit mode; click on one of its endpoints; move it aside a little, then move it to the endpoint of the neighboring polyline and press "V" on the keyboard. This action makes the endpoints of the two neighboring polylines coincident. Repeat with the next polyline until you've paired up all endpoints. Finally, select them all; click the "Join Polyline" toolbutton (or go to Modify|Join Polyline); click the "3D Polyline" icon on the Inspector Bar (or choose "3D Polyline) from the Local Menu; click the Finish flag on the Inspector Bar (or choose "Finish Join Polyline" from the Local Menu.
There are a couple of things you should be aware of:
1. If the existing 3D Polylines don't all lie on a single plane, you may not be able to extrude the result.
2. It's not always necessary to go through the Place on Workplane and connect endpoints procedures, but it's difficult or impossible to tell beforehand whether it will be necessary -- so go ahead and do it.
3. A 2D profile is generally used for extruding. Only rarely is it advantageous to use 3D Polylines for this purpose.