パスワード付きの投稿にアクセス制限をかけるときに使いました。
【rails】投稿にパスワードを設定する方法、url直打ち対策済み

qiita.rb

url = request.url.gsub!(/%21|%22|%23|%24|%24|%25|%26|%27|%28|%29|%2A|%2B|%2C|%2F|%3A|%3B|%3C|%3D|%3E|%3F|%40|%5B|%5D|%5E|%60|%7B|%7C|%7D|%7E|/,
    "%21" => "!", "%22" => '"', "%23" => "#", "%24" => "$", "%25" => "%", "%26" => "&", "%27" => "'", "%28" => "(", "%29" => ")",
    "%2A" => "*", "%2B" => "+", "%2C" => ",", "%2F" => "/", "%3A" => ":", "%3B" => ";", "%3C" => "<", "%3D" => "=", "%3E" => ">", "%3F" => "?", "%40" => "@",
    "%5B" => "[", "%5D" => "]", "%5E" => "^", "%60" => "`", "%7B" => "{", "%7C" => "|", "%7D" => "}", "%7E" => "~")

コピペして使ってね。

参考
https://www.seil.jp/doc/index.html#tool/url-encode.html