of fig1 2 the manipulation of collar 14 illustrated in fig6 may occur for example when a passenger desires merely to lean to his or her right and rest his or her face on a firmly positioned object detailed also in fig3 is base plate 22 u2032 to which collar 14 is connected as well as guides 90 rigidly connected to seat back 86 base plate 22 u2032 is functionally equivalent to base plate 22 albeit slightly different in appearance each of guides 90 is an elongated structure comprising base 94 at each end of base 94 is an outwardly extending flange 98 together with a laterally extending flange 102 collectively each base 94 and corresponding flanges 98 and 102 form a pair of opposed vertically oriented slots into which a slide 18 may be fitted for travel as slide 18 travels within the slots head rest assembly 10 is adjusted vertically with respect to seat back 86 fig7 finally shows slide 18 of the present invention slide 18 has a width w approximately equal to the distance between opposed slots of a guide 90 curved peripheral projections 106 cause the width w of slide 18 to be slightly greater than the distance between the opposed slots however because projections 106 are deformable under pressure slide 18 may readily be fitted into guide 90 projections 106 then bear slightly against outwardly extending flanges 98 of the guide 90 providing adequate friction to maintain slide 18 in a selected position relative to guide 90 should however a passenger desire to.