Олег Батищев

<adminhtml>
                    <rewrite>
                        <catalog_product_helper_form_gallery_content>
                            HB_ProductMedia_Block_Adminhtml_Catalog_Product_Helper_Form_Gallery_Content
                        </catalog_product_helper_form_gallery_content>
                    </rewrite>
                </adminhtml>

...
    <global>
        <models>
            <myarticles>
                <class>My_Articles_Model</class>
                <resourceModel>myarticles_resource</resourceModel>
            </myarticles>
            <myarticles_resource>
                <class>My_Articles_Model_Resource</class>
                <entities>
                    <article>
                        <table>myarticles</table>
                    </article>
                </entities>
            </myarticles_resource>
         </models>
         ...
     </global>