a method that includes : arranging plastic and further workpieces such that an abutment surface of the plastic workpiece is abutted to a first surface on the further workpiece and a projection on the plastic workpiece extends through a through hole in the further workpiece ; linearly moving a friction tool parallel to its rotational axis such that a friction surface on the tool contacts a front surface of the projection ; linearly moving the tool along the rotational axis while rotating the tool so that a pin on the tool penetrates and plasticizes the projection as well as drives a portion of the plasticized projection into an undercut formed in the hole of the further workpiece ; and retracting the tool from the projection .