<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<div style="position: relative; 500px;height: 200px;border: 1px solid red;margin: 0 auto;">
<div style="position: absolute;left:0;bottom:0; 50px;height: 50px;background-color: black;"></div>
</div>
<div style="position: relative; 500px;height: 200px;border: 1px solid red;margin: 0 auto;">
<div style="position: absolute;right:0;bottom:0; 50px;height: 50px;background-color: black;"></div>
</div>
<div style="position: relative; 500px;height: 200px;border: 1px solid red;margin: 0 auto;">
<div style="position: absolute;right:0;top:0; 50px;height: 50px;background-color: black;"></div>
</div>
</body>
</html>