Aggregate forums - How are they done?

[Ryan_C]

Here's that I want to do:

Main Forum
- Sub forum 1
- Sub forum 2

I would like all threads in sub forum 1 and 2 to be displayed in the main forum. So, in essence the main forum is just an aggregate of sub forum 1 and 2. I've seen this done before, but how is it done?

[Zachery]

That is not possible without extensive code modifications. However topic prefixes, and clickable prefixes (via an addon) like how vbulletin.org is setup, might be what you want.