<!doctype html>
<html><head>
<title>Border clipping</title>
<style>
.div1 { width: 50px; height: 50px;
      border: 10px solid black; 
      border-radius: 20px;
      position: fixed;
      left: 50px;
      top: 50px;
}

.div2 {
      width: 40px; height: 40px;
      border: 10px solid black;
      background: black; 
      border-radius: 10px;
      position: fixed;
      left: 55px;
      top: 55px;
}

</style>
</head>
<body>
  <div class="div1"/>
  <div class="div2"/>
</body></html>