<?php

function show_full_width_header_on_boxed_layout(){
    echo '</div>';
    echo '<div class="kleo-page page-boxed">';
}
add_action('kleo_header', 'show_full_width_header_on_boxed_layout', 9999);
function show_full_width_footer_on_boxed_layout($sidebar){
    if($sidebar == 'footer'){
        echo '</div>';
        echo '<div class="kleo-page">';
    }
}
add_action('get_sidebar', 'show_full_width_footer_on_boxed_layout', 9999);