<!DOCTYPE html>
<html lang="en">
<head>
  <title>Bootstrap Example</title>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script>
  <style>
  span {
    display: inline-block;
    width: 70px;
    height: 70px;
    margin: 6px;
    background-color: #555;
  }
  </style>
</head>
<body>

<div class="container">
  <h2>Borders</h2>
  <span class="rounded"></span>
  <span class="rounded-top"></span>
  <span class="rounded-right"></span>
  <span class="rounded-bottom"></span>
  <span class="rounded-left"></span>
  <span class="rounded-circle"></span>
  <span class="rounded-0"></span>
</div>

</body>
</html>

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.