body {background-color:#ddd;}

#wrap {
    width:900px;
    margin:0 auto;
}
#test{width:960px;
height:500px;
background-color:#000;}
.box17{
    margin:2em 0;
    position: relative;
    padding: 0.5em 1.5em;
    border-top: solid 2px black;
    border-bottom: solid 2px black;
}
.box17:before, .box17:after{
    content: '';
    position: absolute;
    top: -10px;
    width: 2px;
    height: -webkit-calc(100% + 20px);
    height: calc(100% + 20px);
    background-color: black;
}
.box17:before {left: 10px;}
.box17:after {right: 10px;}
.box17 p {
    margin: 0; 
    padding: 0;
}