function register_portfolio_sidebars() {

register_sidebar(array(
        'name'      => __( 'Portfolio Item Sidebar', 'raw_theme' ),
        'description'   => __( 'Sidebar used on portfolio items.', 'raw_theme' ),
        'before_widget' => '<li id="%1$s" class="widget %2$s">',
        'before_title'  => '<h4 class="widgettitle">',
        'after_title'   => '</h4>',
        'after_widget'  => '</li>'
    ));

}
add_action( 'widgets_init', 'register_portfolio_sidebars' )