horizontal line in markdown code example

Example 1: how to add horizontal ruler to md

use three or more
asterisks ( *** ), 
dashes ( --- ),
or underscores ( ___ ) on a line

Example 2: markdown horizontal line

***

---

_________________

Example 3: markdown horizontal line

Do this									Don't do this
Try to put a blank line before...		This would be a heading.
										---
---  									Don't do this!

...and after a horizontal rule.

Example 4: markdown straight line

horizontal line in markdown:
---