<!DOCTYPE html>
<html>
<head>
<title>Title of the document</title>
<style>
#box {
height: 70px;
width: 70px;
position: relative;
border-bottom: 2px solid #0004ff;
background: #cccaca;
}
#borderLeft {
border-left: 2px solid #0004ff;
position: absolute;
top: 50%;
bottom: 0;
}
</style>
</head>
<body>
<div id="box">
<div id="borderLeft"></div>
</div>
</body>
</html>