I was asked how the floorboards are held down....
There's a Jamb Cleat on the frame, and a wooden "hook" on the underside of the floorboard.
The cord goes up behind the hook, around the bottom of the jamb cleat, around the cleat and pull.
You can see in the second picture, the Jamb Cleat is simply a piece of wood cut so that where it meets the oak frame, it makes a very narrow triangular gap. As the cord is pulled tight, it traps itself.
Simple as that. There may be better ways, but that's cheap, and it works.