I've been following this blog http://brian-the-techie.blogspot.ca/2013/03/how-to-rig-poser-prop.html and have arrived at this point in my 'gizmo' creation.  The line 'storageOffset' is followed by all zeros in his example but in the book 'Practical Poser 8: The Official Guide' (Chapter 12, page 337) it is written as 'storageOffset 0 0.3487 0'

What does this line do? I'm going to guess that it gives a location for the particular part in relation to other parts, or to 0, 0, 0?  

Nobody really knows what that line does. ;) It's always 0 0 0 when it follows an actor declaration as part of something posable, and it's always 0 0.3487 0 when it follows a prop declaration in a static item. I'd strongly advise sticking to that formula!

I don't have the Poser 8 book, but I imagine the example there is of a prop.

Bloodsong (aka B L Render) thinks storageOffset was intended to do step-and-repeat, for example to make a chain by repeating a single link; but it doesn't work out that way. It seems to offset the rotation centres, but not the actual geometry. It's possibly a broken feature in the Poser syntax, which is not an uncommon occurrence.

Thanks for the informative answer.  I'm surprised that this kind of stuff is documented somehwere...like in the manual that comes with Poser.   I'll file that little tidbit away in my 'Poser secrets' file.

   Thanks again.  

You're very welcome. The syntax of Poser files was never intended for use by anybody other than the makers; the idea of third party content generation only really got going around versions 3 and 4. Ironically, it was the easy "hack-ability" of those plain text files that was partly responsible for making that possible.