Adding divs in WooCommerce Custom Theme

I’ve been trying to add custom div’s to my woocommerce product page, without result. All I’ve been finding is vague documentation pointing me towards “hooks”. So I’ve done everything instructed in these documents. (Copy and create the woocommerce folder within my theme, creating hooks in my functions.php)

Here’s one such hook I wrote, but it’s doing nothing.

function add_borders(){
echo "<div class='corner-left-top'>       </div>";
echo "<div class='corner-left-bottom'>    </div>";
echo "<div class='corner-right-top'>      </div>";
echo "<div class='corner-right-bottom'>   </div>";

echo "<div class='border-left'>           </div>";
echo "<div class='border-right'>          </div>";
echo "<div class='border-top'>            </div>";
echo "<div class='border-bottom'>         </div>";
}
add_action('woo_content_after','add_borders');

I think I’m doing something completely wrong, because it shouldn’t be this hard simply adding divs to a page. Could someone point me in the right direction?