How can I shorten the border right and bottom?

<div class="col-lg-4 col-md-4 col-sm-12 portfolio-img-wrap">
    <img src="images/portfolio/5.jpg" class="img-fluid">
    <div class="portfolio-topleft"></div><div class="portfolio-bottomright"></div>
</div>

.portfolio .portfolio-topleft:before {
	border-top: 2px solid #757575;
	width: 60%;
}
.portfolio .portfolio-topleft:after {
	border-left: 2px solid #757575;
	height: 45%;
}
.portfolio .portfolio-bottomright:before {
    border-bottom: 2px solid #757575;
}
.portfolio .portfolio-bottomright:after {
    border-right: 2px solid #757575;
}