Here is one of the three most used commands while assembling in AutoCAD 3D. The most part of creating a 3D object in AutoCAD is based on seen in 3D.
AutoCAD gives you the ability to create trivial 3D objects with more or less a click, and you will be constructing the less trivial objects by combining the trivial objects using one of these commands: UNION, SUBTRACT and INTERSECT.
The UNION command
This command helps to unite 2 or more objects (2D or 3D) and make them one object.
If we consider the circle and the rectangle below
If we consider that these objects overlap, the red image will be the result of their combination.
The resulting object (in red) now is a single object.
This command works only with solids, regions and surfaces. The following is an object that is built using the combination of a pyramid and a box.
To make the series complete, we are coming soon with the INTERSECT and SUBTRACT command.