3-lines Nav/Menu Icon

markup

<div id="lines" class="btn"></div>

styles

.btn { 
    position: relative;         
    margin-top:2%; 
    border: 2px solid black;
    border-radius: 2px; 
    height: 36px; 
    width:36px;  
}
#lines:before { 
    border-bottom: 17px double black;
    border-top: 6px solid black;    
    content:"";
    height: 5px; 
    position: absolute; 
    right:3px;  
    top: 4px; 
    width:30px; 
}