insert a line to break up text

If what you want is a separator between posts, modify the style.css entry for .hentry at line 531 by adding a border and padding:

.hentry {
border-top:2px solid purple;
margin:0 0 48px;
padding-top:10px;
}

It looks as if the case studies are all one post. If that is the case, you can use a horizontal rule tag to separate them:

<hr class="case-separator" />

Then style the case-separator class in style.css, if necessary.

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