券

Bottom 刀 — the indexing knife radical. Ancient contracts were split into two halves with a knife; each party kept one piece, and the two could later be matched at the cut to verify the agreement. The knife at the base of 券 is literally the tool that made the document binding — a built-in etymology for 'ticket, voucher, certificate.'

Top 龹 — the shared upper element of the 卷 family (卷 roll, 倦 weary, 拳 fist, 圈 ring, 蜷 curl). It supplies the sound juàn → quàn with the regular j/q alternation and carries the 'rolled-up, curled' image at the heart of every member of the series. Here it pictures a rolled-up document — the ancient form of a written contract.