Magento convert quote item to order item

<global>
    <!--convert your custom product attribute "myattribute" from quote item to order item-->
    <fieldsets>
        <sales_convert_quote_item>
            <myattribute>
                <to_order_item>*</to_order_item>
            </myattribute>
        </sales_convert_quote_item>
    </fieldsets>

    <!--add your custom product attribute "myattribute" to quote item-->
    <sales>
        <quote>
            <item>
                <product_attributes>
                    <myattribute />
                </product_attributes>
            </item>
        </quote>
    </sales>

    <!--convert product attribute to quote item through event observer-->
    <events>
        <sales_quote_item_set_product>
            <observers>
                <mymodule>
                    <class>mymodule/observer</class>
                    <method>convertAttribute</method>
                </mymodule>
            </observers>
        </sales_quote_item_set_product>
    </events>
</global>

public function convertAttribute(Varien_Event_Observer $observer) {
    $item = $observer->getQuoteItem();
    $product = $observer->getProduct();
    $item->setMyattribute($product->getMyattribute());
    return $this;
}