plates 12 12 u2032 the width of the adjustable shade rail 30 can be decreased by increasing the amount of overlap between base plates 12 12 u2032 referring to fig5 the overlap of base plates 12 12 u2032 is at its maximum limit and therefore the width of adjustable shade rail 30 is as short as physically possible for this particular embodiment of the present invention the width of the adjustable shade rail 30 can be increased by decreasing the amount of overlap between base plates 12 12 u2032 referring to fig6 the overlap of base plates 12 12 u2032 is at its minimum limit and therefore the width of adjustable shade rail 30 is as large as physically possible for this particular embodiment of the present invention the components of the adjustable shade rail 30 may be constructed of any suitable material including metal plastic or wood referring to fig7 and fig7 a window covering 50 containing the adjustable shade rail 30 is shown window covering 50 preferably includes a shade element 52 which can be any type of shade or blind material known in the art including but not limited to venetian blinds roman style shades and honeycomb cellular shades window covering 50 can also contain control cords 54 which can be any type of control device known in the art including but not limited to an opening cord a raising cord or a securement cord window covering 50 can also have a u201c cordless u201d construction as known in the art in which case the control cords 54 would not be present window covering 50 can also contain brackets 56 which can be any type of device known in the art used.