JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
	<li>
    	<a href="">Link1</a>
        <span></span>
    </li>
	<li>
    	<a href="">Link2</a>
        <span></span>
    </li>
</ul>

CSS

body{ background: #000;}
a{ color: #fff;}
li{ padding: 0px; margin: 0px; list-style: none; display: inline-block; float: left; margin: 10px; position: relative;}
ul{ padding: 0px; margin: 0px;}
li span{
	display: none; width: 1px; background: #fff; position:absolute; bottom: 100%; height: 100px; left: 50%; margin-left: -1px;
}

li:hover span{ display: inline-block;}