如何在导航栏的两边画两条线？

<ul class="navigation">
  <li><a href="#">Home</a></li>
  <li><a href="#">About</a></li>
  <li><a href="#">Services</a></li>
  <li><a href="#">Contact</a></li>
</ul>

.navigation {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: #f1f1f1;
}

.navigation li {
  float: left;
}

.navigation li a {
  display: block;
  color: #333;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
}

/* 添加两条线 */
.navigation:before,
.navigation:after {
  content: "";
  display: table;
}

.navigation:after {
  clear: both;
}

.navigation:before,
.navigation li {
  box-sizing: border-box;
}

.navigation:before {
  border-top: 2px solid #333;
  border-bottom: 2px solid #333;
  width: 100%;
  margin-top: 10px;
  margin-bottom: 10px;
}

<ul class="navigation">
  <li><a href="#">Home</a></li>
  <li><a href="#">About</a></li>
  <li><a href="#">Services</a></li>
  <li><a href="#">Contact</a></li>
</ul>