How to post anonymously?

Hiyaa, I wanted to post something anonymously, but I can't seem to find the checkbox for the "reply anonymously" thing. I posted something anonymously in the thread earlier, but now I can't find the checkbox. Would highly appreciate any help Xx

Some forums allow anonymous posting, whilst some do not. This one, for example, does not. In which forum were you trying to post anonymously?

I don't really know how to see which forum it's in. But I've posted in that thread anonymously, and the OP is anonymous. When I come and tried to post anonymously again, on the same thread, the checkbox wasn't available

Edit: I figured out how to see which forum the thread is in. It's in Faith and Spirituality

Thanks. You can't post anonymously in Faith and Spirituality (in fact you can't post anonymously in most forums). However, I note that the most recent thread in that forum, islam- man made?, was started anonymously and contains anonymous replies. That would seem to contradict what I've just said.
My guess is that this thread was created in a different forum initially, where anonymous posting was allowed, and has since been moved by the mods into Faith and Spirituality (given the topic of the thread). I note that there have been no anon posts to it since 16:37 yesterday, so it was presumably moved shortly after then.