A little help?

Try this

Wire10ga - THANKS! May I ask what I did wrong or how it was repaired?

Thanks for the tip. I will try that on my next design.

I usually use NetFabb and do a manual repair.  Here is a step-by-step on how to do this:

Right Click on the model, then select EXTRAS, Repair part. on the upper tool bar select shell selector.  Click the Red body, then click the "flip triangles" icon on the toolbar.  This flips your main body surface triangles which were inverted (red)

Rotate model so you can see the bottom.  The red traingles shouldn't be there, it should be open.  Select the surface selector in the tool bar, then click on the "remove selected triangles" icon.

Zoom in on the piece so you can get a better view of the inside of your guide.  It too has a flipped surface.  Select the "surface selector" tool, then click on the  "flip triangles" icon.

Now you're left with a few open edges and holes (yellow dashed lines).  Rotate model so you can get a better view. Select "stitch triangles" from the actions tab. then click OK on the popup window.  This will get rid of the open edges around the square opening.  NOTE:  If you were to click on "close holes" instead, you would have refilled the opening.

Next click on the close holes, to close the remaining holes of the model.  All the yellow lines are now gone, and the model is clean.  Click on apply repair and Yes on the remove old part.

Done!

very cool! thanks. need more like this those youtube guides are impossible to follow fast as they go.
how do you insert pics instead of just uploading links? thats what I cant figure out. cant even find how to seperate parts of quotes or add more than 1 in post

I would very much like to see this in the WIKI.
NICE JOB!

yes. at least how to use the free version to best of its ability. I have several models others made and didnt line up corners etc to make a closed layer but had some edges just a bit off and look closed. the default fixes dont fix these right and mostly just fill in the voids. this is an easy error when using Sketchup to design things it seems. its like designing in 123Design and forgetting to group parts that need to be made as 1.

I know I would sure like more info on how to use this tool.  I'm sure I only use about 1% of what it can do. So anything you can provide would be appreciated.