Source
File: wp-admin/includes/dashboard.php
function wp_dashboard() {
$screen = get_current_screen();
$columns = absint( $screen->get_columns() );
$columns_css = '';
if ( $columns ) {
$columns_css = " columns-$columns";
}
?>
<div id="dashboard-widgets" class="metabox-holder<?php echo $columns_css; ?>">
<div id="postbox-container-1" class="postbox-container">
<?php do_meta_boxes( $screen->id, 'normal', '' ); ?>
</div>
<div id="postbox-container-2" class="postbox-container">
<?php do_meta_boxes( $screen->id, 'side', '' ); ?>
</div>
<div id="postbox-container-3" class="postbox-container">
<?php do_meta_boxes( $screen->id, 'column3', '' ); ?>
</div>
<div id="postbox-container-4" class="postbox-container">
<?php do_meta_boxes( $screen->id, 'column4', '' ); ?>
</div>
</div>
<?php
wp_nonce_field( 'closedpostboxes', 'closedpostboxesnonce', false );
wp_nonce_field( 'meta-box-order', 'meta-box-order-nonce', false );
}