A masonry wall is a wall made from materials, which have traditionally been cemented together with the use of mortar. Masonry walls can be non-structural fences or structural walls in buildings or retaining walls in landscaping. They are commonly built with block CMUs (concrete masonry units) or with brick or stone. A retaining wall can contain rebar and be filled with concrete. Masonry walls may be straight or serpentine. They can incorporate columns and caps, seats, niches and buttresses. They can be highly decorative with a mortar bond and a variety of materials and patterns. They can be rustic and laid as a rubble wall. Flat stones without mortar can be laid as a dry wall.