Extrude: output back?

Hello.
Is there a way of outputting back polygons during extrusions? To create a watertight mesh, for example?

Below is the simplest of all examples. A plane that's been extruded. Poly extrude displaces the selected polygon and creates walls around it, but does not create the back face. As a result we get a hollow box.

Currently only by using "Shell", which will work for your example, but is limited in that if extrusion is from non-planer mesh, then "shell" will extrude only by "Normal direction" and not by "Manipulator direction".

I had been looking at creating a composite tool for a "Shell extrude" But it does not look possible with current tools available that can be used it composite, or with how sub_selections are stored/pasted.

Have been playing.

Have made a composite tool (attached).
Import composite and add an hotkey(or add it to a streamline tool). Select an object(it must be a open surface), and execute composite tool. It wiil make a small extrusion(the same as shell) but will leave polygon selection you can move with manipulator.
There will be an un-used material left behind after running the tool, as I have had to use that to temp store sub_object selection.

Hope it is OK for what you want. If not, don't use it 

Thank you Steve, I gave the tool a try and it does exactly what I need. The extrusion amount seems to be fixed, but with local transformations I can push extruded polygons further along their normals or even make them to follow cursor (like in ExtrudeCursorDirection), so that's no problem at all.
Thanks again for your time.

PS. Nice workaround with the material.

The extrusion amount seems to be fixed,

Yes, the only way to make it interactive is to force the "P_" function value popup window. Not good for workflow.

Thanks again for your time.

No problem, I was making the tool anyway, well, very similar. What I wanted was a "Shell Extrude", to select polygons on a model, then extrude that selection into its own solid object. You can do that will the composite tool I posted, just a need to add at the beginning of the tool functions a "P_Duplicate Selected Polygons"(<-with default settings).

PS. Nice workaround with the material.

The only thing I could do lol. When welding(even same mesh), the saved/stored sub_selection is lost (also groups are automatically removed). But mateial zones are left in tact.