<div class="square">
  
</div>

.square {
  width: 441px;
  height: 441px;
  background: linear-gradient(
        to right,
        black 33%,
        transparent 33%,
        transparent 66%,
        black 66%
      )
      no-repeat 0 0 / 100% 20px,
    linear-gradient(
        to right,
        black 33%,
        transparent 33%,
        transparent 66%,
        black 66%
      )
      no-repeat 0 100% / 100% 20px,
    linear-gradient(
        to bottom,
        black 33%,
        transparent 33%,
        transparent 66%,
        black 66%
      )
      no-repeat 0 0 / 20px 100%,
    linear-gradient(
        to bottom,
        black 33%,
        transparent 33%,
        transparent 66%,
        black 66%
      )
      no-repeat 100% 0 / 20px 100%,
    red;
/*   border: 1px dashed #3b3838; */
}