Draggable table: drupal_render, render, both yield an empty string for "#weight" types?
Weight objects can be rendered with form_process_weight()

    $weight = array(
        '#type' =&gt; 'weight',
        '#title' =&gt; t('Order'),
        '#default_value' =&gt; $i,
        '#delta' =&gt; 1,
        '#attributes' =&gt; array('class' =&gt; array($table_id . '-weight'))
    );

    $weight = form_process_weight($weight);