[Cook] What does "single-thread" do anyway?

[Fredrick Paul Eisele]

I know I could read the source code, but ...

I understand how "single-thread" is intended to be used.
What I need is for a lock for processes external to aegis.
(Yes, this has been discussed before.)
What I am wondering is if I could use...

boofar.lock: phoey
  single-thread boofar.lock
{
    ... do some stuff...
}

Does "single-thread" use file locking?

If so, then I could use flock( boofar.lock )  to prevent the
external program from doing what I don't want it to do.

Thanks