A cavity door roller is a type of door opener that allows you to open the door from inside the room. It has a roller that is attached to the wall, which helps you to push open the door. Cavity Door Rollers are used in commercial and residential buildings. They are mostly found in bathrooms, but they can also be found in other rooms such as closets and pantries. Cavity Door Rollers have been around since 1884 when they were first introduced by William Thomas Greenough