U+21A8 "↨" Up down Arrow with Base Unicode Character

U+21A8 "↨" Up down Arrow with Base is a typographic symbol depicting a vertical line with an upward pointing arrowhead at the top and a downward pointing arrowhead at the bottom, anchored by a short horizontal base line. It is officially categorized as an arrow symbol and is often used in technical diagrams, signage, or user interfaces to indicate bidirectional vertical movement or alignment, such as in elevator buttons, mechanical controls, or computational flowcharts where a stable reference point is implied. Its design distinguishes it from simpler bidirectional arrows by the base, which emphasizes a fixed origin or baseline for the two opposing directions.