.wrapper {
  display: grid;
  grid-template-columns:
    [full-start] 1fr [wrapper-start]
    minmax(0, 70rem) [wrapper-end] 1fr [full-end];

  /* Optional gap */
  column-gap: var(--pad, 1rem);
}

.wrapper > * {
  grid-column: wrapper;
}

.wrapper > .full-width {
  grid-column: full;
}