Abstract: An improved workbench table top cut away at a corner to provide a rectangular rabbet, and having an extension arm extending across the corner below the top surface of the table. A U-shaped clamping member includes an elongated arm adjoining outer and inner legs, and is disposed in a plane parallel to the table top around the extension arm. The extension arm includes a hole spaced from its end. A brace bar of similar but slightly smaller dimensional cross-section as the hole joins the legs through the hole. A conventional adjustment means such as a screw is utilized to adjust the clamping member relative to the extension arm along an axis of adjustment. Narrow extensions in the elongated arm are fitted in cooperatively shaped slots in abutting portions of the legs, and pins extend orthogonally through the legs and arm extensions. A first rail extends from the extension arm across the rabbet and is fixed to the opposite side thereof, and is disposed against and in sliding contact with the brace bar.