I can't find anyhow to let members, on a per-forum basis, to be able to lock their own threads. Would be useful, as some of my sites have classifieds sections, and locking a thread is a good way to indicate that whatever was on offer is now over. Would be nice if this were a feature in the permissions.
There's no way to do this with the default permissions, but this add-on should allow you to achieve those goals.
FYI... I haven't tested this add-on myself, but I've read the thread and seen your specific requests were possible.