The Falcon 9 fairing uses four pneumatic pushers to impart a positive separation force between the fairing halves. The pushers all mount on half of the fairing and push against the other half.
But there is an odd feature on these pushers that I can't understand. The pusher rods are hollow, and on the other half of the fairing are needle pins that clearly fit inside the rod bore.
The picture below has the pusher cylinders on the left (green circles) and the needle pins on the right (orange circles). You can see the tips of the hollow cylinder rods in red. I'll try to post a better picture of them, but trust that they are hollow.
Why would they do this? The legs have pushers and there the rods have solid ends to push against a plate on the legs. The interstage has pushers and these have solid ends to push against brackets on the backside of the second stage.
So the leg and interstage pushers didn't need hollow rods. Why did the fairing? What is the purpose of fitting needle pins through the rods of pneumatic pushers?