What kind of tool do I need to remove this?

[jmaxwell]

Question in the title. I want to remove this bleed valve from the radiator in the first picture. It appears I need some kind of long slotted tool. Any ideas?

Diameter 1/2"

 

[Madrab]

A drag link socket (basically a really large screwdriver socket) would do it, not got one of them? I'd get in there with a pair of vice grips, if that doesn't work then chap it round with a screwdriver. Alternatively make up a tool with a piece of sheet steel cut wide enough to fit the gap.

 

[jmaxwell]

Sorted now, thanks. Thin piece of metal stuck in a small vice and used like a screwdriver did the trick.