How to illustrate multiple threads in sequence diagram?

I found this question on Google and wasn't a huge fan of the accepted answer so I just came up with my own. This is how I represented the threading model in my application (my organization calls it the 'Concurrency Viewpoint'):

Hopefully it helps someone.

Here is one diagram that may be useful, and on the left-hand side you can see the explanation: http://sdedit.sourceforge.net/multithreading/example/index.html