A mechanism for opening and closing an angularly movable panel, comprising a drive box for attachment to a fixed frame, the drive box housing a cable wheel rotatable upon translation of a control cable when in operative association therewith, a chaincase having a sprocket operatively connected with a chain located in a casing, the chain being for attachment at one end to an angularly movable panel, rotation of the sprocket effecting translation of the chain into, or out of, the casing in accordance with the sense of sprocket rotation, the chaincase being mountable in any of four different positions on the drive box.