JSFiddle - React, Tailwind, and code Playground

HTML

<div class="content">
    <h1>Some content</h1>
</div>

CSS

.content {
    width: 50%;
    height: 2000px;
    margin: 0 auto;
    position: relative;
    background: white;
}

.content:before {
    content: "";
    display: block;
    width: 50px;
    height: 200px;
    position: absolute;
    left: -50px;
    background: red;
}