All you need is two gradients, one to define the horizontal lines and the other the vertical ones:
.container {
width: 398px;
height: 198px;
margin: 0 auto;
background:
repeating-linear-gradient(to right,
transparent 0 calc(50px - 2px),
#fff calc(50px - 2px) 50px),
repeating-linear-gradient(to bottom,
transparent 0 calc(50px - 2px),
#fff calc(50px - 2px) 50px)
red;
}
<div class="container">
</div>
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…