zig Tryit Editor

<!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 href="../../cdn.jsdelivr.net/npm/bootstrap%405.3.3/dist/css/bootstrap.min.css" rel="stylesheet">
  <script src="../../cdn.jsdelivr.net/npm/bootstrap%405.3.3/dist/js/bootstrap.bundle.min.js"></script>
  <style>
  span {
    display: inline-block;
    width: 70px;
    height: 70px;
    margin: 6px;
    background-color: #f9f9f9;
  }
  </style>
</head>
<body>
<div class="container mt-3">
  <h2>Border Width</h2>
  <p>Use .border-1 to .border-5 to change the width of the border:</p> 
  <span class="border border-1"></span>
  <span class="border border-2"></span>
  <span class="border border-3"></span>
  <span class="border border-4"></span>
  <span class="border border-5"></span>
</div>
</body>

</html>