Help with an Eagnas 112 for a beginner

Hi

I am a total novice to stringing but acquire myself an old Eagnas 112 machine
I am a little lost as to how the aluminium disc work
If anyone have experience and can just give me a brief idea as what to do, it will be much appreciate.
The lever seems to work but it does not lock the horizontal bar
i am also lost as to how the two bolts work with the disc and the horizontal bar

See attach
http://www.eagnas.com/lilylee/eag112.html

Where alse I can get another set of Stringer universal V shape side frame support?

Thanks