A corner bracket apparatus for a slidable frame includes a body having first and second arm portions depending therefrom, the first and second arm portions being oriented generally orthogonally relative to each other and adapted for insertion into respective first and second hollow framing members of said slidable frame, the first arm defining an outboard side edge and an inboard side edge generally opposite the outboard side edge and an internal pocket positioned therebewteen. The corner bracket apparatus further includes a lifter member pivotably coupled to the body and generally received in the pocket, the lifter member having a contact portion adapted to bear against a runner along which said slidable frame is adapted to slide, the lifter member being pivotable between an advanced position in which the contact portion is proud of the outboard side edge of the first arm, and a retracted position in which the contact portion is generally shy of the outboard side edge of the first arm.