Updated installation method. Advanced underfloor inspection port Evolve the traditional model for faster installation. Underfloor inspection port for improved stability and strength. In conventional models, the outer frame is used to install the pan, but the plastic cradle is used to reduce the pier. In addition, the sliding structure of the plastic cradle allows the root to be held closely and firmly in place. In addition, the interior lid installation method and rotating handle have been renewed to allow for easy and stable installation.