Create a div that is the line with the code like this:
CSS
div#lineHorizontal {
background-color: #000;
width: //the width of the line or how far it goes sidewards;
height: 2px;
display: inline-block;
margin: 0px;
}
div#block {
background-color: #777;
display: inline-block;
margin: 0px;
}
HTML
<div id="block">
</div>
<div id="lineHorizontal">
</div>
<div id="block">
</div>
This will display a block with a horizontal line to another block.
On mobile devices you could use (caniuse.com/transforms2d)