I think your friend was referring to boning. Boning is plastic these days, although I think it actually was bones originally. Here is some I removed from 2 gowns I recently made over. Both were lined, and the boning slipped into casings in the lining that held it all in place.
I haven't worked with boning much , so I recommend searching YouTube for techniques.
You should be able to buy boning at places that sell fabrics and supplies for formal wear.
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