: 6px solid;
  }
  h3 {
    column-span: all;
    outline: 1px solid blue;
  }
  a {
    position: absolute;
    width: 1em;
    height: 1em;
    background-color: blue;
  }
  </style>

  <fieldset>
    <legend>Legend<a></a></legend>
    <div class="inner">
      <div>block1</div><div>block2</div><a></a>
      <h3>spanner<a></a></h3>
      <div>block3</div><div>block4</div><a></a>
    </div>
  </fieldset>
</html>
