JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

div {
  position: relative;
  background: #eee;
  width: 25px;
  height: 25px;
  margin: 30px 0 0 30px;
}
div:before {
  position: absolute;
  width: 10px;
  height: 25px;
  top: 0;
  left: -10px;
  content:"";
  background: #222;
}
div:after {
  position: absolute;
  width: 10px;
  height: 25px;
  top: 0;
  right: -10px;
  content:"";
  background: #222;
}