| 摘要 |
An apparatus for reducing air drag against an apparently flat message surface when the message is intended for day or night viewing from approximately directly in front or behind. Symbols comprising the message, or their backgrounds are inclined backwards as louvers to allow free air passage. The symbols or their backgrounds may be placed on a plane behind and parallel to the apparent message surface, and viewed through hole(s) cut in that surface, with a gap between the two planes allowing air flow. Night-lights above each symbol may be provided to ensure accurate night viewing.
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