Small retainer walls can be used for a variety of reasons. Under a Lapa or next to and around a Boma it can be used as extra seating. Using a foam cushion on top of the wall, the retainer wall is seen as seating and not just as a wall.
Other reasons for a retainer wall can be to assist in keeping the garden soil from eroding away or guiding rain water away from a potential flooding area. Retainer walls can also enhance the aesthetics of the garden, lapa or entertainment area.