/* Keyword value */
grid-row-start: auto;

/* <custom-ident> values */
grid-row-start: somegridarea;

/* <integer> + <custom-ident> values */
grid-row-start: 2;
grid-row-start: somegridarea 4;

/* span + <integer> + <custom-ident> values */
grid-row-start: span 3;
grid-row-start: span somegridarea;
grid-row-start: 5 somegridarea span;

/* Global values */
grid-row-start: inherit;
grid-row-start: initial;
grid-row-start: revert;
grid-row-start: revert-layer;
grid-row-start: unset;

This property is specified as a single <grid-line> value. A <grid-line> value can be specified as:

• either the auto keyword
• or a <custom-ident> value
• or an <integer> value
• or both <custom-ident> and <integer>, separated by a space
• or the keyword span together with either a <custom-ident> or an <integer> or both.

auto

Is a keyword indicating that the property contributes nothing to the grid item's placement, indicating auto-placement, an automatic span, or a default span of 1.

<custom-ident>

If there is a named line with the name '<custom-ident>-start', it contributes the first such line to the grid item's placement.

Note: Named grid areas automatically generate implicit named lines of this form, so specifying grid-row-start: foo; will choose the start edge of that named grid area (unless another line named foo-start was explicitly specified before it).

Otherwise, this is treated as if the integer 1 had been specified along with the <custom-ident>.

<integer> && <custom-ident>?

Contributes the nth grid line to the grid item's placement. If a negative integer is given, it instead counts in reverse, starting from the end edge of the explicit grid.

If a name is given as a <custom-ident>, only lines with that name are counted. If not enough lines with that name exist, all implicit grid lines are assumed to have that name for the purpose of finding this position.

An <integer> value of 0 is invalid.

span && [ <integer> || <custom-ident> ]

Contributes a grid span to the grid item's placement; such that the row start edge of the grid item's grid area is n lines from the end edge.

If a name is given as a <custom-ident>, only lines with that name are counted. If not enough lines with that name exist, all implicit grid lines on the side of the explicit grid, corresponding to the search direction, are assumed to have that name for the purpose of counting this span.

If the <integer> is omitted, it defaults to 1. Negative integers or 0 are invalid.

The <custom-ident> cannot take the span value.

grid-row-start = 
  <grid-line>  

<grid-line> = 
  auto                                                |
  <custom-ident>                                      |
  [ [ <integer [-∞,-1]> | <integer [1,∞]> ] && <custom-ident>? ]  |
  [ span && [ <integer [1,∞]> || <custom-ident> ] ]   

HTML

<div class="wrapper">
  <div class="box1">One</div>
  <div class="box2">Two</div>
  <div class="box3">Three</div>
  <div class="box4">Four</div>
  <div class="box5">Five</div>
</div>

CSS

.wrapper {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-auto-rows: 100px;
}

.box1 {
  grid-column-start: 1;
  grid-column-end: 4;
  grid-row-start: 1;
  grid-row-end: 3;
}

.box2 {
  grid-column-start: 1;
  grid-row-start: 3;
  grid-row-end: 5;
}

Result

• Related CSS properties: grid-row-end, grid-row, grid-column-start, grid-column-end, grid-column
• Grid Layout Guide: Line-based placement with CSS Grid
• Video tutorial: Line-based placement