Check out example codes for "acf true false field default value". It will help you in understanding the concepts better.

Code Example 1

<?php 
    $show_sidebar = get_post_meta($post->ID, 'show_sidebar', true);
    if($show_sidebar === '' || $show_sidebar === '1'): ?>
<div id="sidebar">
<?php if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar('Sidebar') ) : ?><?php endif; ?>
</div>
<?php endif; ?>

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