A curtain rod assembly comprises a set of telescoping tubes running between brackets and a locking assembly for setting the length of the telescoped tubes. The locking assembly comprises a screw body, attached to the end of the smaller inner tube, which has a tapered screw along which a captive expansible sleeve moves. The sleeve may be a split cylinder with spring elements running across the gap of the split. When the tubes are twisted relative to each other, the sleeve moves lengthwise along the tapered screw and expands radially outwardly to lock the assembly; and simultaneously with the locking action there is a desirable small change in the length of the tube assembly. The screw body is reversible within the tube assembly, so the rod assembly can be used in applications where the rod both pulls inwardly on, or pushes outwardly against, a window frame.