Description:
Its made from a block of wood, covered in a lot of wood glue for a smooth finish, and two pieces of aluminum tubing.
The alu tubes are different diameters so that the smaller slides inside the bigger one. The one with the wood attached is the inner part.
The inner part has one hole for the screw that goes into the notches, and a long cut that limits up/down movement later on.
The outer part has a big hole (6mm) and a small hole (the one with the pencil mark). The other small hole was the setting for the old notches.