Vectorworks has some really cool 3D tools, and it's tempting to always look at these…
Vectorworks Tip #189 – 3D Modelling – Subtract Solids
Subtract Solid is like the opposite of Add Solid. Instead of joining to solid objects together, this command will use one object to subtract from the other. So the technique is to make sure you create the base object, then create the subtracting object, and then subtract it from the base. This technique works extremely well when you need to create a complex object. You will find it easier to create a complex object if you use two simpler objects and subtract them.