<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>JS Bin</title>
</head>
<body> <div class="div1"> <div class="div2"></div> </div> </body>
</html>
.div1{
border:solid 1px red;
width:100%;
height:400px;
position:relative;
margin-top:80px;
}
.div2{
border:solid 1px red;
width:100%;
height:60px;
position:absolute;
margin:auto;
bottom:; right:;
box-sizing: border-box;
border-left:none;
border-right:none;
border-bottom:none;
}
http://jsbin.com/miciburuwo/1/