how to add wall cutout to an object?

Hi Bakie,
Thank you for this. Following your idea, I've been trying to turn a window in to a fireplace. So far I have extracted the fireplace object tuning and added its Tuning and TuningID in the window's Object Definition - which resulted in a window with a menu option to light it, but when I try my sims just wave and show a crossed out footsteps icon above them. So I tried extracting and adding the footprint, then rig and slot from the fireplace. Each time entering them in to the Object Definition, as I think that will make the object use them. The window does now place like a fireplace, but otherwise the inability to access it to light is the same. I'm out of ideas for now, but maybe will think of more later. If you, or anyone else has any ideas they'd also be welcomed I am considering making the fireplace out of two objects, one cloned from a window and the other cloned from a fireplace. A bit clunky, but maybe workable. It would also give me the option of glass fronts. Earlier experiments with moving the fire effect of the fireplace proved it could be placed anywhere I wanted - even really far away from the actual fire, so I should be able to place it in the recessed area behind the wall.