Trying to add a vertical border to post 'header'.

EDIT: ‘Border’ does not refer to css borders here.

I’m re-working automattcs _s or the underscore theme and seem to have hit a dead end.
The title and meta of the blog posts are shown in a separate box. I did that by simply adding background, outline and box-shadow to .entry-header, so the html and css are pretty unchanged.
Now what I’m trying to do is to add a border along the left side of this box and have the title and meta text to stay next to it (not pop under it).
Putting a div just below <header class=”entry-header”> in content.php and styling it with:

#entry-border{
	width: 20px;
	height: 50px;
	position: relative;
	top:-2px;
	left:-7px;
	background: white url('images/pattern.gif');
	float:left;
       }

…and floating the post title (#entry-title) left as well, kind of works but breaks with long titles. Neither will the border adapt to the ‘entry-header’ box height (% or inherit makes it disappear).
Any attempt of moving the meta row results in a mess.
For some reason, background-image won’t work here if no-repeat is set.

Here’s a link to the original github files, since I’m working locally.

I hope I’m making sense.