Is this an isolation valve?

[TNDU]

On one side of a cabinet is this valve, pictured, which looks like an isolation valve ( /elbow) and the other side is the pipe connecting to it, which then leads to the gas fire.

There is gas supply to the fire so if this is the isolation valve, it is in the open position.

I can't work out why the straightline across the valve, indicated with the red arrow, where you can insert your flat screwdriver head is in a horital position rather than a vertical position? I would have thought that it should be in a vertical position to be open?

 

[Stuckinarut]

Looks like a restrictor elbow, so doesn't matter which orientation the screw is in.

 

[TNDU]

Looks like a restrictor elbow, so doesn't matter which orientation the screw is in.

I see, thank you.

So to restrict the gas flow, you turn that screw clockwise? And if you turn it clockwise fully, it would shut the gas off to the fire to allow servicing?