One end of the hair is
hooked to the end of the bow. The other is tied to the handle of the
bow. The florcent string pictured here is obviously not traditional.
The two parts of the bow slide together.
The bow is tensioned while playing by how the muscian holds it. The following is my best guess at how to hold it. I'm sure I'm horribly wrong.
In fact, here's an hold (colorized) photograph of how it should be held:
