.navbar-nav li a::before {
content: ' ';
display: block;
width: 1px;
height: 70%;
background: #fff;
position: absolute;
bottom: 15%; /* it makes me center */
left: 0;
}
/* uncomment if you want to hide first stripe
.navbar-nav li:first-child a::before {
display: none;
}
*/
Replies to 70-percent heigth vertical stripe 
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