Add horizontal line button to WordPress's editor has provided a little snippet of code that will add a “horizontal rule” (or <hr />) button to the default editor in WordPress.

What’s a horizontal rule? It’s one of these lines:

In my opinion, that should definitely be a default button in the WP editor, but since it isn’t, you can use WPSnipp’s little snippet and add it to your installation. Cool!

WordPress – Add horizontal rule button to editor –