Sanderson front standard locking system?

[Eero]

Hello,
I’m making a copy, or a version of Sanderson field camera, and i have figured out every other functions, but the front standard locking system in this type of Sanderson, and the purpose of those red marked tabs.
There is the other type of locking system where a screw attached to the front standard presses onto the focusing rack, but this is something else.

Here, as the earlyphotography.co.uk says: a lever, with 'O' shaped handle, clamps the front standard to the side of the focusing rack.

But how does it do that?
Does somebody have the actual camera in hand?

The other question is what are those tabs for?

I would appreciate very much any tips.