A wall unit is one of the components that make up modular fitted bathroom furniture. In the diagram below the rest of the components have been faded-out to highlight the wall units.
Standard wall units are usually available as single or double units. In this image the single unit on the left and double unit on the right flank a central mirror.
Wall units tend to be slightly shallower than base units and can be given a "one-piece" look by adding bridging panels top and bottom. The door on a single unit can usually be fitted to open on the left or right hand side but double unit doors are hinged on the outside only as shown. A panel might be required to finish of the side of the unit if it is visible if the carcass is a different colour to the door of the bathroom furniture. Some are available with mirror doors negating the need for a separate mirror.