I have a template that I would like to modify in SketchUp. As you can see from the attached .stl file, it is a plate with cutout for a GoPro camera. I would like to make the cut out about an eighth of an inch larger. I have tried selecting the interior faces to push in, but they are start at 0 mm and will not let me push in. I can pull faces upwards (making the plate thicker), but I am trying to trim around this outline just a bit. Any suggestions? I would like to avoid using the eraser tool so that I don’t accidently erase lines I need.
From your narrative I suspect that the Offset Tool may give you the result you are looking for. But I cannot open your .stl to check it. If you have an importer plug-in already installed can you post the SketchUp file here instead?
After importing the STL file into SketchUp, you need to get rid of the triangulation. ThomThom’s CleanUp3 will make quick work of that. Then you should be able to select the edges around the opening and use Offset followed by Push/Pull to get rid of the waste.
If you import with the merge coplanar faces option on, it comes in cleanly with no triangulation issues. But how large is the original supposed to be? You need to know that to choose the right units during import. I used mm (default) and the whole thing is only 3/8" across, so a 1/8" offset seems wrong! Anyway, you need to trace one edge of the cutout to create a face because otherwise the offset tool will try to use the outer edge of the whole thing! Then it is easy to offset and pushpull the extra through to enlarge the cutout.
Edit: it looks like cm might be the right units. Also, it is a component, so don’t forget to open it for edit before you start trying to modify it!