I've found a few nice components by Jcb121 at http://sketchup.google.com/3dwarehou...2035&scoring=m

But the closest I can get to a model of KJN's 45 x 90 aluminium extrusion that many seem to use is http://sketchup.google.com/3dwarehou...da&prevstart=0 which I've compared to the diagrams on KJN's website and it seems to be an exact match to their 45x90 (heavy) extrusion, except that it is missing the four cavities just inside the corners. However if one orbits to the cross-section on the opposite end of the model, these cavities are detailed there correctly but not pushed/pulled as "nothing" through the extrusion if that makes any kind of sense...

I've tried to modify these cavities into the model/component... but as a SketchUp (CAD?) newbie of just a few days standing have been spectacularly unsuccessful, and am not even sure if this can be done with the free version of SketchUp.

Would anyone know how to do this?

Cheers,
Andy

PS. The reason I'm trying to do this is that I'm questioning whether I would be able to easily attach the SBR20 Rail to this extrusion using self-tapping screws into these cavities?