// can someone please evaluate the code here to understand why "product" and "portfolio" not behave the same on the URLs?
// after Testing and ReTesting again, i understand that product doesn't work for singluar "single.php" or "single-product.php"
// meaning "domain.com/product/" and "domain.com/product/post/" take use of archive-product.php
// but if i rename archive-product.php to archive-products.php the url "/product/" does use the archive.php but..
// "/product/post/" show warning of " failed to open stream: No such file or directory"

$labels = array(
        'name' => _x('Products', 'post type general name'),
        'singular_name' => _x('Product', 'post type singular name'),
        'add_new' => _x('Add New', 'book'),
        'add_new_item' => __('Add New Product'),
        'edit_item' => __('Edit Product'),
        'new_item' => __('New Product'),
        'all_items' => __('All Products'),
        'view_item' => __('View Product'),
        'search_items' => __('Search Products'),
        'not_found' => __('No products found'),
        'not_found_in_trash' => __('No products found in the Trash'),
        'parent_item_colon' => '',
        'menu_name' => 'Products'
    );
    $args = array(
        'labels' => $labels,
        'description' => 'Holds our products and product specific data',
        'public' => true,
        'menu_position' => 5,
        //'hierarchical' => true,
        'supports' => array('title', 'editor', 'thumbnail', 'excerpt', 'comments'),
        'rewrite' => array('slug' => 'product'),
        'has_archive' => true
    );
    register_post_type('product', $args);

$labels = array(
        'name' => _x('My Portfolio', 'post type general name'),
        'singular_name' => _x('Portfolio Item', 'post type singular name'),
        'add_new' => _x('Add New', 'portfolio item'),
        'add_new_item' => __('Add New Portfolio Item'),
        'edit_item' => __('Edit Portfolio Item'),
        'new_item' => __('New Portfolio Item'),
        'view_item' => __('View Portfolio Item'),
        'search_items' => __('Search Portfolio'),
        'not_found' =>  __('Nothing found'),
        'not_found_in_trash' => __('Nothing found in Trash'),
        'parent_item_colon' => ''
    );

    $args = array(
        'labels' => $labels,
        'public' => true,
        'publicly_queryable' => true,
        'show_ui' => true,
        'query_var' => true,
        'menu_icon' => get_stylesheet_directory_uri() . '/article16.png',
        'has_archive' => true,
        'rewrite' => true,
        'capability_type' => 'post',
        'hierarchical' => false,
        'menu_position' => null,
        'supports' => array('title','editor','thumbnail')
    );
    add_theme_support('post-thumbnails');
    add_image_size('single-post-thumbnail', 400, 9999);
    register_post_type('portfolio', $args);

    register_taxonomy(
        "Skills",
        array("portfolio"),
        array(
            "hierarchical" => true,
            "label" => "Skills",
            "singular_label" => "Skill",
            "rewrite" => array('slug' => 'portfolio')
        )
    );