Thanks for the reply and adjustments. I've got a lot to learn, but it seems trial and error is the best way.
When I create an STL from your file, and from another project I was working on, I still get:
i.e.
137 faces exported (number varies)
0 lines exported (all are showing 0)
400 objects ignored. (numbers vary)

I guess my questions is- which of the 3 pieces of info is for information only, or are any of these 'error' messages I should be concerned with.

(I don't have a 3D printer yet to try these out as far as printing compatibility.)

skp file of my project

Hope I did the posting correctly.

Just joined this forum hoping it will be a valuable place to get help and help others (once I am more up to speed).

Running Windows / Free version of Sketchup.
Designed a 'product'- basically a box with a few 'holes and walls'. It checks out as being 'closed' (no red surfaces) in CADSpan's preview. I tried to create an STL file using STL import / export and get the following message:
157 faces exported
0 lines exported
526 objects ignored.

Noy sure how to take this...!
Is my model a disaster, does it have minor issues, or.... what!?