A traction battery pack assembly includes, among other things, first and second pieces of an enclosure having an interior area. An attachment rim is disposed at a periphery of the first piece. The attachment rim has a stand-off that includes a platform portion and turned flange. The platform portion extends outward from the interior area in a first direction. The platform portion provides an aperture. The turned flange extends away from the platform portion in a second direction and terminates at an end face. The second direction is transverse to the first direction. The aperture is configured to receive a fastener that clamps the end face against the second piece.