<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<div class="container">
<div class="row" style="magin-bottom: 30px;">
<div class="col-md-6" >
<div class="item-grid col-md-12" style="height:120px">1</div>
<div class="item-grid col-md-12" style="height:100px">3</div>
<div class="item-grid col-md-12" style="height:130px">5</div>
</div>
<div class="col-md-6" >
<div class="item-grid col-md-12" style="height:100px">2</div>
<div class="item-grid col-md-12" style="height:20px">4</div>
<div class="item-grid col-md-12" style="height:120px">6</div>
</div>
</div>
<div class="row">
<div class="item-grid col-md-6" style="height:120px">1</div>
<div class="item-grid col-md-6" style="height:100px">2</div>
<div class="item-grid col-md-6" style="height:100px">3</div>
<div class="item-grid col-md-6" style="height:20px">4</div>
<div class="item-grid col-md-6" style="height:130px">5</div>
<div class="item-grid col-md-6" style="height:120px">6</div>
</div>
</div>
