HTML

border corner frames image css

<style>
.corners {
  position: relative;
  width: 50px; /* for demo purposes */
  padding: 10px;
}

.top, .bottom {
  position: absolute;
  width: 20px;
  height: 20px;
  pointer-events: none;
}

.top {
  top: 0;
  border-top: 1px solid;
}

.bottom {
  bottom: 0;
  border-bottom: 1px solid;
}

.left {
  left: 0;
  border-left: 1px solid;
}

.right {
  right: 0;
  border-right: 1px solid;
}
</style>
<div class="corners">
  <div class="top left"></div>
  <div class="top right"></div>
  <div class="bottom right"></div>
  <div class="bottom left"></div>
  content goes here
</div>