In architectural terminology, the dado, borrowed from Italian meaning die or plinth, is the lower part of a wall, below the dado rail

Dado rail

A dado rail, also known as a chair rail, is a type of moulding fixed horizontally to the wall around the perimeter of a room.The dado rail is traditionally part of the dado and, although the purpose of the dado is mainly aesthetic in modern homes, the dado rail still provides the wall with...

 and above the skirting board.
This area is traditionally given a different decorative treatment to the upper part of the wall; for example panelling

Panelling

Panelling is a wall covering constructed from rigid or semi-rigid components. These are traditionally interlocking wood, but could be plastic or other materials....

, wainscoting or lincrusta

Lincrusta

Lincrusta is a deeply embossed wallcovering. A British invention, it was the brainchild of inventor Frederick Walton who earlier patented linoleum floor covering. Lincrusta was launched in 1877 and was used in a host of applications from royal homes to railway carriages. The linseed gel continues...

. The purpose of the dado treatment to a wall is twofold: historically, the panelling below the dado rail was installed to cover the lower part of the wall, which was subject to stains associated with rising damp; additionally the dado rail (also known as the chair rail) provided protection from furniture, in particular the backs of chairs. In modern homes, the dado treatment is generally aesthetic.

The name derives from the architectural term for the part of a pedestal between the base and the cornice.