Process of thread lock?

I have seen threads that are locked. Do the users do it to their own created threads or are the moderators the only one who can do it? If the users do it, can somebody teach me how?

Locking a thread won't stop it from being reported as spam if it is spam

Locking a thread just means that your question is answered and doesn’t need more answers. For example, if you are the creator of this thread, there would be a mint green button that says “Lock Thread” and press it. When you press it, nobody will be able to comment on it anymore. Don’t worry, if you lock a thread, it won’t reduce your xp or do any harm to your gamehag profile.

And to answer your question, people who are the creators of their own threads can lock if any time.

I don't see any green button. Is there a difference between the mobile app vs. the actual website?