div {
display: grid;
grid-template-columns: 1fr 1fr;
grid-gap: 10px;
}
.container {
display: grid;
grid-template-columns: repeat(4, 1fr);
grid-template-rows: repeat(2, auto);
gap: 1.75rem;
width: min(90%, 68.5rem);
margin-inline: auto;
}
.wrapper {
display: grid;
grid-gap: 1rem;
grid-template-columns: 1fr 1fr 1fr;
grid-auto-flow: dense;
padding: 1rem;
}
.box {
background-color: red;
color: #fff;
border-radius: 0.5rem;
padding: 1rem;
font-size: 200%;
}
.a,
.d,
.e,
.f {
background-color: green;
grid-column: span 2; /* <-- here is the trick */
}
<div class="grid-container">
<div class="grid-item">1</div>
<div class="grid-item">2</div>
</div>
.grid-container {
display: grid;
grid-template-columns: auto auto;
}