Quote Originally Posted by Bob F.
Not a silly question: I used to wonder exactly the same thing....

They are used when rotating the head. In the "-" position they provide click-stops (rather than an actual lock) to centre the head vertically. In the "O" position, the click-stops are disengaged to allow easy rotating of the head.

At least, that's in my enlarger - it is possible that they are supposed to lock and that mine are damaged....

Cheers, Bob.
Thanks Bob!
In my instruction manual (copy), 'finally', I found the sentence: "Operate the locking lever (8) at either side to allow the enlarger head to engage inthe 90 position; Then secure the enlarger head again with the locking knob(9)".

At one side he's doing that correctly, at the other he doesn't click. A little investigation will be necessary! :-)

Do you have also the VLS version?
How can we controle the quality of the vc filters numbers?
With stepwedge? How to proceed?

Many thanks!