Abstract: A mutiple-purpose assembly clip for assembly of radiant ceiling panels and/or for flattening bowed radiant ceiling panels. The clip uses a "twist-lock" technique. In a first rotational position the clip is positioned over the panels. The clip is then rotated about an axis perpendicular to the panels to a second rotational position to cause flanges on the clip to engage corresponding channels on the panels, thereby to urge adjacent panels together. A "mirror image" clip is also used which twists in the opposite direction for locking. The clip includes a central cutout in a U-shaped member to form defined flanges and edges. The cutout is dimensioned so that as an alternative to use for locking adjacent panels (where the cutout fits over edge connections of the panels) it can fit over a fluid-carrying tube mounted on the rear of the panel. This permits the clip to be mounted wholly on one ceiling panel for flattening the panel.