<div class="s">sample</div>
.s { width: 200px; height: 200px; background: #ccc; background-image: linear-gradient(45deg, #f00 10px, transparent 0), linear-gradient(-45deg, #f00 10px, transparent 0), linear-gradient(135deg, #f00 10px, transparent 0), linear-gradient(-135deg, #f00 10px, transparent 0); }