Vine trellis fan shapes are popular because they symbolize the growth of the plant striving for progress. On windowless and other slightly structured surfaces they can be-- individually or in a group-- an enrichment. In edge areas, etc., they can be constructed asymmetrically (see 6060). On highly articulated/structured facades (with windows, cornices, etc.), fan forms often have a disturbing effect; in most cases, climbing aids with only vertical and horizontal lines are preferable because they "absorb" the existing structures and uphold/continue the design. A diagonal design language is then up to the plants and their instincts, which thus naturally 'blur' the grid/net of the trellis. Fan shapes are ideal for many plants, except for strong twiners like wisteria. Please refer to the sections on climbing plants and planning aids.