Horizontal Rule not showing in posts!

Hi guys

I have an issue. I don’t want to use the read more tag in my post but a simple <hr/> tag to load up a horizontal line. The problem is that I have tried this several times but the line never shows.

What am I doing wrong?
I even added the following code in my CSS to make it hopefully work:

.post hr {
display: block;
}

Nothing seems to work. Please I just want a horizontal line to break up big chunks of content into more readable content blocks.