as tile hardwoods carpeting and the like in a preferred embodiment the frictional surface may include a rubberized surface in other embodiments the frictional surface may include a textured surface in a preferred embodiment the upper tubular member 10 is received within the lower tubular member 12 one or more of apertures 24 are defined through the lower tubular member 12 in a spaced apart relation and substantially perpendicular to a longitudinal axis of the lower tubular member 12 the upper tubular member 10 may also have one or more cooperating apertures 26 defined through the upper tubular member 10 and are similarly defined in a spaced apart relation and aligned substantially perpendicular to a longitudinal axis of the upper tubular member 10 a bolt or pin 18 is received through the apertures 24 of the lower tubular member 12 and the cooperating apertures 26 of the upper tubular member 10 the bolt or pin 18 includes a hole 22 defined through a transverse axis of the bolt 18 that is adapted to receive a retaining pin such as a cotter pin 20 the length of the door security device may be selectably adjusted by the user selecting the appropriate aperture 24 and cooperating aperture 26 to obtain the desired length of the security device the length of the device is adjustable to accommodate the height of the doorknob 36 with respect to the floor surface 38 the.