Well, I installed mine in about 45 minutes. Here's what I did: Put a piece of masking tape on both the center of the valance and diffuser and marked the center point. Used 2 of the plastic pieces for locating the holes on the two middle side holes. I put the plug into the hole the two pieces of masking tape faceing up on each piece. I then held the diffuser in place and pushed against it to stick the tape against the valence. Then remove the diffuser and the hole locaters are taped in place. Mark the holes and drill them a bit oversized - I went 3/8". Then use two screws and fasten the diffuser to check your positioning. If you are satisfied, remove it...use 3M molding tape around the edge of the diffuser - just inside the small edge lip (1/8"). Remove the backing and stick it in posistion. Then screw in the two screws and you are done. The screws hold the diffuser up and the 3M molding tape holds the edges tight against the valence - and you only have to drill 2 holes. You can also easily get at both of them from inside the valence so you don't have to remove it. Piece of cake.l
