With the release of WordPress 3.6 not long ago, there was the addition of a new feature called “Post Locking,” which automatically locks a post that’s currently being worked on.
But that description doesn’t really cover all the flexibility you get with Post Locking. You can actually easily “break into” a locked post too – which is also important.
But breaking into a locked post is not like breaking into a post that was being worked on pre WordPress 3.6. In fact, it ends up being a completely different experience.
WordPress Pre Version 3.6