Aaaargh!

She Who Must Be Obeyed wanted a mirror above the dining room fireplace.

After the walls have been painted.

Not so bad if you frame the mirror like a picture and hang it like one.

On the other hand...

If you want to attach it directly to the wall without any sort of mechanical fastener...

Then you need some way to hold it in place while the adhesive cures.

I tried many approaches to avoid putting holes in the freshly painted mill work.

But no joy.

So I ended up with this.

Now I get to patch the holes and repaint.

And you can't just touch up the spots because you can never get the sheen to match quite right.  You have to paint the whole surface to a natural edge.