栈 here means 'warehouse / storage shed' (as in
货栈 huòzhàn, warehouse), not 'inn' or 'plank-road'. In modern logistics,
栈单 often shows up as a negotiable instrument — like a bill of lading but for stored, not shipped, goods. Hong Kong and Taiwan trade documents still use it; mainland filings increasingly say
仓单 (cāngdān).
