<nav>
	<ul>
		<li><a href="#">nav01</a></li>
		<li><a href="#">nav02</a></li>
		<li><a href="#">nav03</a></li>
	</ul>
</nav>

nav ul {
	display: flex;
}
nav ul li {
	list-style-type: none;
}
nav ul li:not(:last-of-type)::after {
	content: "";
	width: 1px;
	height: 15px;
	background-color: #999;
	margin: 0 2em;
	display: inline-block;
	position: relative;
	top: 3px;
}