Threading - Baton Object That Routines Can Pass Around?

This will no doubt sound like a pretty dumb question to some, but, despite having written many useful single-thread apps over the years, I don't understand enough about threading yet.

Consider this scenario:

There are four modules, each on its own thread, that can happily run concurrently most of the time. However, each module occasionally causes a few seconds' intensive disk activity (by design) and it would be more efficient (faster, less fragmentation) if only one module at a time wrote to the same physical drive.

It would be useful to have something like a baton that modules within a given scope can pass around, perhaps dependent on their respective priority levels.