silverstripe-framework/templates/Includes/GridFieldToolbarHeader.ss

<tr class="title">
	<th colspan="$ColumnCount">
		<% if $Title %><h2>$Title</h2><% end_if %>
		<div class="right">\$DefineFragment(toolbar-header-right)</div>
		<div class="left">\$DefineFragment(toolbar-header-left)</div>
	</th>
</tr>