i wrote a custom module, which includes a phtml placed at

\app\design\frontend\mytheme\default\template\checkout\cartrelated\cartrelated.phtml

i added a line

    <block type="cartrelated/cartrelated" name="cartrelated.cartrelated" 
template="checkout/cartrelated/cartrelated.phtml"></block>

in

\app\design\frontend\mytheme\default\layout\checkout.xml

the phtml not displaying, anyone know what is the problem?

config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Rayman_Cartrelated>
            <version>0.1.0</version>    <!-- Version number of your module -->
        </Rayman_Cartrelated>
    </modules>
    <global>
        <blocks>
          <cartrelated>
            <class>Rayman_Cartrelated_Block</class>
          </cartrelated>
        </blocks>
        <models>
          <cartrelated>
            <class>Rayman_Cartrelated_Model</class>
          </cartrelated>
        </models>
    </global>
</config>

the cartrelated.phtml just contains echo 'abctest'