A bow visor is a feature of some ships, in particular ferries and Roll-on/roll-off ships, that allows the bow to articulate up and down, providing access to the cargo ramp and storage deck near the water line. In modern ferry design over the last 25 years, though, bow visors have given way to clam doors that act like a clamshell and are believed to be safer than bow visor doors. There have been several recorded incidents in which bow visors have partially opened whilst the ship is in motion, resulting in the some ships having to put in to have their visor locking mechanisms strengthened.