.container {
  width: 400px;
  height: 300px;
  float: left;
  margin: 40px;
  background: #999;
  border-radius: 5px;
  box-shadow: 0 8px 15px rgba(0, 0, 0, 0.6);
  background: linear-gradient(top left, #333, #bbb);
  position: relative;
  overflow: hidden;
}

.container::after {
  content: "";
  width: 400px;
  height: 300px;
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  transition: opacity 0.3s;
  background: -webkit-repeating-linear-gradient(
    -45deg,
    rgba(0, 0, 0, 0.3) 4px,
    rgba(0, 0, 0, 0.3) 8px, transparent 8px,
    transparent 12px
  ), 
  -webkit-repeating-linear-gradient(
    45deg,
    rgba(0, 0, 0, 0.3) 4px,
    rgba(0, 0, 0, 0.3) 8px, transparent 8px,
    transparent 12px
  );
}

.container:hover::after {
  opacity: 0;
}