Abstract: A screw-in post support for use in supporting a post vertically above the ground. The post support has a four-sided post-receiving box mounted atop a shaft having a helical blade affixed thereto. Opposed rectangular slots are provided in two of the walls adjacent the floor of the box. The slots are dimensioned to allow the insertion of a rectangular piece of lumber in order to provide the necessary torque to screw the post support into and out of the ground. A pair of adjacent walls may be equipped with flanges that may be drawn toward one another to clamp the box around a post.