I don't even know how to search for this ... if it's been answered please point me to it and I apologize if this is a duplicate.

When I do 3D shapes I generally use the primitives, and almost always a box, because it's simple. A problem I run into though is that if I then rotate that shape it no longer has the size I originally gave it, but now its size is the rectangle that bounds the rotated box.

For example, a 5.5"W x 8'L x 1"H box rotated 45° along the Z-axis is no longer that but is now a box that is 5' 11-49/64" square.

But in the real world, if I rotate an 8' 1x6 45° I still have an 8' 1x6, it's just at a 45° angle to perpendiculars.

Is there any other shape I should be using that still provides the true real-world dimension regardless of rotation? Or should I be doing something other than rotating the 3D box?

Where this becomes a problem is if I want to extend that 8' 1x6, or cut it. I can't say "I need another foot" and simply add 1', I have to do math.

Can anyone help?

Thanks.