Presspull
From AutoCAD 2007 a brilliant new 3D command arrived. It's called Presspull. If you have made a 3D box and want to make a hole through you can do that with PRESSPULL. First you create a rectangle with a polyline on top of 1 face on the 3D box. Next you activate PRESSPULL command and click inside the rectangle. Now you can make a hole by pulling the face on the rectangle inside the box. You can use this command for the existing faces of an object, or by imprinting additional faces on an object and pulling those inside or outside. If you pull it outside of the box, then you create a solid object pointing out from the 3D box. You can also use 3D POLYLINE instead of polyline. First align UCS so it's parallel with the side you are making a hole. Scroll down on this page to see tutorial "Creating a Wall with Polysolid".