Ah, now I understand.
I have just read the tutorial and that is a pretty interesting way to model, sort of like self assembly furniture but still having to build your own parts. http://www.geekatplay.com/pnina/PicnicTable/PicnicTable.pdf
It is one of the good features of Carrara that you can build things in the assembly room on the fly when you need a quick prop.
To follow the tutorial you don’t really need the collision detection, just eyeballing things should be close enough (By the way, the quickest way to duplicate a small number of parts is with Ctrl-D and then moving the part to where you want it. Pressing Ctrl-D again IMMEDIATELY after moving it, without clicking away, will reproduce the part again with the same movement applied. Then Ctrl-D again and so on).
I do recommend for static props that you learn to model entirely in the vertex room, you can insert the primitive shapes in there and modify them directly. That way your completed model will be one whole object.
The Carrara6 manual that is in ‘Program Files\DAZ 3D\Carrara8\Carrara Help\CarraraOnlineHelp’ is still valid for vertex modelling and the Carrara7 manual should be available for download somewhere.
Searching for ‘Carrara Vertex modelling’ on Google gives some useful hits for Carrara as well as generally useful vertex modelling tips.