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The minimum adequate size is 8' high by 12' wide backboard (3 panels). Attaches to two tennis court fence posts which, on most tennis courts, are spaced 10' apart. 16' wide (4 panels) and 20' wide (5 panels) backboards require 3 tennis fence posts for attachment. A 16' backboard, if posts are standard, expose more channel and hardware. It is not as aesthetically pleasing. Typically 3 or 5-panel models have minimal hardware and channel exposure.
If posts are 8' apart, a 16' wide backboard can be elegant. 20' wide backboards are very popular, especially in the 10' high series. Bakko feels a 12' backboard is adequate if only 1 person hits.
If occasionally or potentially 2 people may practice, a 16' backboard is recommended. If 2 people hit and elegance is important, a 20' backboard is a must. Schools and tennis camps sometimes purchase 6, 7 and 8-panel kits, several panels for a continuous wall.