The right-hand end of the Tool bar contains the Quick Preferences. These are Vectorworks and…
Vectorworks Tip #023 – Preferences – Use Occluded Selection and Snapping
This is a Vectorworks preference that will speed up the way that you work in 3D by making it easier to snap only to the parts of the model that you see. Instead of snapping being based on the stacking order, the snapping will be based on the way that the objects appear in the view.