Cacher is the code snippet organizer for pro developers

//Inside of the original single.php, delete everything and replace it with this:

<?php
$post = $wp_query->post;
if (in_category('4')) {include(TEMPLATEPATH . '/single-15.php');
}
elseif (in_category('3')) {include(TEMPLATEPATH . '/single-16.php');
}
else {include(TEMPLATEPATH . '/single-1.php');
}
?>