This adjustment mechanism/assembly for a backrest/headrest includes a series of parts connected by a threaded rod with a knob on each end. The parts are arranged such that they sandwich two support members so that when the knobs are loosened the unit can easily slide up and down, changing the elevation of the backrest/headrest pad unit with respect to a seat bottom or seat back. Further, when the knobs are loose the upper member and its attached pad can be pivoted fore and aft and slide back and forth. Tightening the two knobs locks the entire unit in place.