Thanks - got it working.

Old AutoCAD user again. For factory layouts it's useful to have pieces of equipment defined as 3D models with their 2D footprint part of the same model but on a different layer. Once the model ('block' in AutoCAD, 'component' in Sketchup) has been inserted into the drawing you can toggle between a full 3D view of the factory and a drawing of 2D footprints which includes things like door swings and access clearances. However it seems that in Sketchup after I insert the component it responds only to changes in the visibility of the layer it was inserted upon, even though integral bits of the component are on other layers. Is there any way to simulate the AutoCAD behaviour?

Thanks, perfect.

Great, thanks. But how do I find the coordinates of a point?

I'm a former AutoCAD user and miss some features. If I have a component floating in space instead of on the floor where it belongs, I want to interrogate a point on that component to find its 3D coordinates then move it relative to its current position specifying the xyz displacements as 0,0,-z where z is the distance the component is floating above the ground plane. Can I do this in Sketchup? (Using Sketchup 8 Free on Windows XP)