Abstract: An apparatus for installing a frame and related appurtenances incorporating, among other elements, four corner members slidably and releasably joined with height and width adjusters. The apparatus may be used in the plurality of assembly activities that require the assembly of a frame, including, but not limited to, cabinet making, furniture making, window framing, trimming, and installation, and door framing, trimming, and installation. Each corner member includes two sections that are substantially orthogonal to one another and may be foldable so that they are substantially parallel when in the folded position. Additionally, each member may be formed with a trim piece mounting ledge to provide a surface to abut a frame trim section to assure a uniform reveal, and stop, hinge, and strike templates. The apparatus frame members may be formed with a unique thickness, or may include trim setback members, to accommodate varying jamb material thickness and the desired reveal.