Here you can see the keyboard frame.
A little puzzle to assemble, not that hard once you figured which part goes where.

On the middle, you have the balance pins : they will make the keys able to move up and down.
They were extremely hard to hammer into the frame - I even hammered my thumb during the process ^^'
On the top, you can see the guide pins : they are here to stop any side movements of the keys.

The black things are just a thin cloth you put to avoid sound when the keys come back to their initial position and hit the wood.