Fan shapes are popular in trellis design 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 disruptive 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 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.