silverstripe-framework/templates/forms/CheckboxSetField.ss

<ul id="$ID" class="$extraClass">
	<% if Options.Count %>
		<% control Options %>
			<li class="$Class">
				<input id="$ID" class="checkbox" name="$Name" type="checkbox" value="$Value"<% if isChecked %> checked="checked"<% end_if %><% if isDisabled %> disabled="disabled"<% end_if %>>
				<label for="$ID">$Title</label>
			</li> 
		<% end_control %>
	<% else %>
		<li>No options available</li>
	<% end_if %>
</ul>