The appearance of brick and stone masonry owes as much to the character of the mortar joints as to the stone and bricks themselves. Unsuitable repointing can affect not only the look but also the durability of masonry, and is amongst the most frequent causes of damage to the character and fabric of historic buildings. The comprehensive repointing of a building is rarely necessary. Generally only those parts that are most exposed to the weather or are affected by specific problems such as leaking rainwater pipes or gutters are likely to be in need of attention. Sound historic mortar should be left undisturbed as it can be an important part of the character and significance of a building. This guidance, aimed at homeowners and non-specialist building professionals, provides a brief technical guide to the key issues and stages that need to be considered when repointing brick or stone walls of older buildings.