How to illustrate multiple threads in sequence diagram?

Question

How can you clearly illustrate multiple threads of execution in a sequence diagram or similar diagram?

I haven\'t been able to find any clear examples. All diagra

Answer 1

I like @Brandon's answer. That's a diagram that shows a clear threading communication model.

I also came across this document which has several different approaches https://www.omg.org/ocup-2/documents/concurrency_in_uml_version_2.6.pdf