A head restraint for a seat being adjustable in a vertical direction, and angularly adjustable with regard to lateral portions of the head restraint. A mechanism providing this adjustability is a linear and rotational locking mechanism with a shaft and a slide. The slide is selectively slidably and rotatably mounted on the shaft. The slide has a locked state which linearly and rotationally fixes the slide on, and with respect to, the shaft. The slide has a release state where the slide is linearly and rotatably movable on the shaft. The slide is fixable in a plurality of linear and rotational positions on the shaft in the locked state. The number of linear and rotational positions on the shaft is considered infinite since for all practical purposes, the slide is not restricted to individual discrete positions, but is continuously adjustable to practically any linear and rotational position.