HTML

<nav class="top-nav">
  <div class="row">
		<div class="large-12 columns">
			<section class="top-bar-section">
				<ul class="left">
					<li class="current"><a href="/">Home</a></li>
					<li><a href="#">Forum</a></li>
					<li><a href="#">Reviews</a></li>
				</ul>
				<ul class="right">
				    <li><a href="#">ActivTrax</a></li>
				    <li><a href="#">Newsletter</a></li>
				    <li><a href="#">Contact</a></li>
					<!--<li><a data-reveal-id="myModal" href="#">Become a Member</a></li>-->
				</ul>
			</section>
		</div>
	</div>
</nav>

SASS

@media #{$small} {
  .top-nav {
		section {
			ul {
				border-left: 1px solid #4D4D4D;
				border-right: 1px solid #4D4D4D;
				li {
					border-bottom: 1px solid #4D4D4D;
					border-top: 1px solid #1A1A1A;
					&.current a {
						color: #b12323;
					}
				}
				&.right {
					border-bottom: 5px solid #dcdcdc;
				}
			}
			a {
				border-top: none !important;
			}
		}
	}
}