<!DOCTYPE html>
<html>
<head>
    <style>
    .box {
        margin: 10px;
        width: 200px;
        height: 200px;
        background-color: green;
    }
    .obscurer {
        position: absolute;
        background-color: gray;
    }
    </style>
</head>
<body>
    <div class="box"></div>
    <div class="obscurer" style="height: 20px; width: 210px; left: 18px; top: 200px;"></div>
    <div class="obscurer" style="height: 210px; width: 20px; left: 210px; top: 10px;"></div>
</body>
</html>