a clip is provided for affixing a construction unit to a building structure . the clip comprises : a generally planar middle portion , an exterior portion located on an exterior side of the middle portion and an interior portion located on an interior side of the middle portion ; the exterior portion comprising a groove at an exterior end of the clip for receiving a construction unit flange , the groove having a generally u - shaped cross - section , the groove defined at least in part by a pair of generally parallel groove portions and a base portion connecting the groove portions at a base of the groove , the base of the groove spaced apart from an opening of the groove ; the middle portion extending from an interior side of groove toward the interior portion ; and the interior portion at an interior end of the clip , the interior portion extending from the middle portion at an obtuse angle to define a fulcrum at a junction between the middle portion and the interior portion .