From a client email:
I am having trouble with the nape of my wigs. Where should the adjusters sit behind the ear or below and under the occipital bone? Note: I have a very narrow head.
The nape should be below the occipital bone, unless the back of your head is flat. (Heather has that issue due to having a fuller neck, for instance.)
The adjusters should be ideally above this, somewhere comfortably in between the bottom of the back of your ears and the top of the nape on the wig. This will differ from woman to woman, though, since it all depends on your head size and how far you let those adjusters in or out.