Cylinder Desk lid
This is the screw that the metal trammels pivot on. The original screw holes were worn out and had to be patched with new wood. Here you can see the lid in the closed position.The metal trammel is fasten to the lid by screws and pivots on one screw at the bottom.
When the lid is opened the pigeonholes are exposed and the lid retracts. Notice the stop where the trammel meets a small angled block of wood on the side of the pigeonholes.