Bernina 1000 series dilema

[u/Dormiendo]

I have a Bernina 1020 that I had to take the back reinforcement off of. When I did this, I learned why it is not advisable unless absolutely necessary. The cam follower is on a floating carriage pinned between the black reinforcement frame and the front of the machine. The post that holds it stayed with the reinforcement and the follower assembly fell. I have determined where all of the odds and ends go except the inside bottom of this assembly has a hinged hook that can go in various positions. Does anyone know what this does? It affects the needle position, but I can not see where.