I often use Moi to model custom boxes to keep things in.
My usual approach is to create two rectangles (Closed curves) representing the outside and inside edges of the box, select both and planar the space between them. This planar surface is then extruded upwards to make the sides. I then select the outer of the two closed curves and extrude it down (Cap Both Ends) to create the base.
Then I often want to move the outer closed curve (which I have extruded to create the base) to the top of the box to help make the lid.
If I select just the closed curve and move it up, the extruded base moves with it - even though I have not selected it. This happens even if I hide the base before selecting and moving the curve.
If I Boolean Union the sides to the base to create one solid, then the closed curve moves alone.
Why does moving the selected closed curve cause the solid extruded from it to also move?
I attach a simple version to illustrate.

History" is a feature to many operations. What you describe is the history mechanism.

To do what you want, you want to jump through one extra step at the beginning and "disable history"

Select item and click on history-disable update

Michael could answer one question for me i always avoided answering with trial and error.... "WHICH" of the items follow the history. So in the situation described here, disable history on the "Curve" works? Or disable history on the "Extrusion" works?

I always selected ALL objects involved in the originating operation and disable history update on all of them and moved on.

Knowing the hierarchy would be helpful for future.

[EDIT] I just read the help reference which tells me the disable operates on the "Resulting surface or solid"? So not the originating curve?

Hi Burr, yep turn history updates off on the extruded solid, not original curve.

I'll see about putting in a way to turn history off by default.

- Michael

Sorry I'm being stupid, where is the option to turn history on and off? After selecting the solid where do I turn the history on or off?

OK thanks -- found it. never explored that corner of MOI before.