The Twenty Ten theme only comes with one default menu, which is included in the header. However the theme also supports multiple menus, thanks to the use of register_nav_menus(). Here’s a quick tip on how to take advantage of this function and add a second menu to the Twenty Ten theme.
Watch the Screencast
Open the functions.php file and look for:
// This theme uses wp_nav_menu() in one location.
The next line is where we see the register_nav_menus() being used. As you can see this function accepts an array.
register_nav_menus( array( 'primary' => __( 'Primary Navigation', 'twentyten' ), ) );
primary: this is a key, or name of the menu, this name should be unique within the array
__( ‘Primary Navigation’): this is the vaule of the key, or description of the menu
To add the second menu simply add another key (menu name) and assign a value (enter description) into the array. Here’s an example of what it can look like when adding your second menu:
register_nav_menus( array( 'primary' => __( 'Primary Navigation', 'twentyten' ), 'secondary' => __( 'Secondary Navigation', 'twentyten' ), ) );
This technique can be used in creating other free themes or child themes as well. If you have any questions, feel free to ask in the comment.