A support assembly comprises a hub slidably coupled to a crossbar to support a sprinkler. A pair of opposed clip assemblies comprising a frame and a bracket couple the crossbar to the ceiling channel on either side. The frame comprises an opening that supports one end of the crossbar, a skirt with an elongated slot, and a leg that extends over the channel. The bracket couples to the frame to lock the clip assembly on the ceiling channel. The bracket comprises a ridge at one edge and a flange at an opposite edge. The ridge is configured to couple to a sidewall of the ceiling channel, and the flange is configured for a user to compress and tighten the bracket. A pair of opposing clamps on either side of the bracket ensures that the frame is securely coupled to the ceiling channel.