Abstract: A fixing element for connecting materials of relatively low strength includes a unitary, one-piece plastic body. An external thread is formed on the plastic body for compressing and compacting the low strength material in the thread turns of the external thread. A first external thread portion has a taper at one end of the plastic body. A second portion has a taper at another end of the plastic body, while a third portion has no taper and extends between the first and second external portions. A penetration tip is connected to the smaller diameter end of the first external thread portion. Further, a stop collar is provided at the large diameter end of the second external thread portion. The penetration tip preferably is a self tapping screw made of a harder material than the plastic body. Further, the thread depth of the second external thread portion decreases along the second external portion as the second external portion approaches the larger diameter of the screw.