to chisel; to bore a hole; to dig or excavate

a metal tool with a sharp blade for carving or cutting; a chisel (now usually referred to as 凿子 záo​zi)

(literary) certain; authentic; irrefutable, as in the word 确凿 què​záo

a hole or socket cut into a piece of wood or stone to receive a matching part; a mortise (often in the idiom 方枘圆凿 fāng​ruì​yuán​záo)