准 borrowed its flatness from water: the full form 準 has water under the bird, naming the water-level tool carpenters used. What is level is reliable; what is reliable is 准 — accurate, on target, permitted to proceed.
准 stamps Chinese officialdom: 批准 'approved' is the two-character verdict every application waits for. In daily speech 准时 'on time' is the politeness that matters most at Chinese dinners — arrive 准时 or text ahead.
A bird 隹 standing on ice 冫 — perfectly level, perfectly ACCURATE.
天气预报不准 'the forecast is inaccurate' may be the most-said sentence about Chinese weather apps — 准 is the bar everything is measured against.