To enable "Read more..." feature in articles body. It works only on mobiles.
With read_full_article enabled in engine settings the horizontal rule in entry editor will act as break point for "Read more..." button.
On mobile this will look like on image below. Of course you can style it as you want.
When enabled there will read_full_article property in Bootstrap object on post page on mobiles only. If article has horizontal line, it will be set to true, otherwise false.
Noticeable difference will be also that content above the horizontal rule is in brief and brief_full properties meanwhile the entire article content is in body and description properties.
Here is an example how you can use it in code: