title: Two divs, one with border rounded other with border rounded inverted
body: <p>I'm trying to create a guide component and need help. How can I have an identical border to this (using CSS):</p>
  
  <p><img src="https://i.stack.imgur.com/qBgxb.png" alt="Tabs Google Chrome"></p>
  
  <p>Anyone know of any strategy, any way to do this, what should I study?
  Thanks</p>