KEY (Heb. maphtēah, opener). An Oriental key was made of wood, with nails or wooden pegs to fit corresponding holes in the bolt holding the door fast (Judg.3.25). Figuratively, a symbol of authority, carried on the shoulder (Isa.22.20-Isa.22.22). Greek kleis, “something that shuts” (Luke.11.52); symbolic of the authority given to Peter (Matt.16.19), but which Jesus still retains (Rev.1.18; Rev.3.7); the key that keeps destructive forces (Rev.9.1) and Satan (Rev.20.1) in the bottomless pit.
International Standard Bible Encyclopedia (1915)
Made of wood, usually with nails which fitted into corresponding holes in the lock, or rather bolt (Jud 3:25). Same is rendered "opening" in 1Ch 9:27.