Lockshield valve

[PaulRobs]

Hi I’ve had a couple of new radiators fitted in a bathroom and need to balance the system.

The lockshield valves look like the photos below, am I missing something but how do you adjust these valves as there’s no spindle as normal valves?
Thanks

 

[cross thread]

Allen key

 

[ianmcd]

you just screw the central allen nut in

 

[gas112]

very liable to leak when touched