Macbook pro, the latest gen. What is the purpose of the bottom bar on the spacebar? The top one slides into the clips and then the the spacebar snaps to the white things, but what's that bottom bar do? I see it slides into the holes, but there's nothing for it to clip to on the space bar and if you push it in too far the white things can't collapse when you press the spacebar down. Explanation? Or at least what to do with the bar? TIA.